The Quick Read: A HELOC can fund an ADU build, but the lenders that write it depend on whether the line sits on your primary home or on a rental, and no single list of banks fits every borrower, because equity, credit, and property type decide who says yes. Lendmire is a mortgage broker, so it names no lenders. It explains how these lenders think and matches your file to a program through its wholesale network.
- A line on a primary residence is the widely available version. On Lendmire’s network it reaches 90% CLTV only at a 720 or better credit profile, on lines up to $500,000.
- A line on an investment property is a narrower product. On this network it caps at 70% CLTV, needs at least a 700 score, and tops out at $500,000.
- The line is sized on what the property is worth today, not on what it will be worth with the ADU finished.
- ADU rent generally counts toward the permanent loan only after the unit is permitted, finished, and documented.
- The usual plan is a HELOC for the build, then a DSCR refinance once the unit is rented.
Key Terms Defined
ADU (accessory dwelling unit): A second, smaller living space on the same lot as the main house, such as a backyard cottage, a garage conversion, or an attached suite.
Granny flat: Another name for an ADU, often used when the unit houses a relative.
HELOC (home equity line of credit): A revolving line secured by your property. You draw money as you need it and pay interest on the drawn balance.
CLTV (combined loan-to-value): Your first mortgage plus the new line, divided by the property’s value.
Draw period: The stretch when you can borrow from the line and payments are interest-only. A repayment period follows, when the balance amortizes.
DSCR (debt service coverage ratio): Monthly rent divided by the monthly payment on the property, including principal, interest, taxes, insurance, and HOA dues.
Certificate of occupancy: The local sign-off that a finished unit is safe and legal to live in.
How large a line the equity supports.
An equity line is sized by combined loan-to-value, occupancy, and credit — not by rental coverage. Switch the occupancy or the credit band and the ceiling moves with it.
Investment-property lines require a 700 minimum credit score; second-home lines start at a 640 minimum and primary-residence lines at 600, and the combined-LTV ceiling steps down as the credit band drops on primary-residence and second-home lines and holds on investment-property lines; the line cap steps down on primary-residence lines and holds at every tier on investment-property and second-home lines.
A debt-to-income ratio above 45% requires 680+ credit. Profiles under 640 are limited to single-family homes. At least 75% of the approved line is drawn at closing. Ceilings, floors, and caps update from Lendmire’s centralized guideline source.
Line estimate
Illustrative estimate only — not a quote, Loan Estimate, approval, or commitment to lend. The rate is an editable assumption; equity-line pricing is variable through both the draw and repayment periods and never converts to fixed. Occupancy and credit drive the ceiling together: an investment property tops out at 70% combined LTV (minimum credit 700, line cap $500,000); a second home tops out at 90% combined LTV (minimum credit 640, line cap $500,000), with the ceiling stepping down as the credit band drops (the cap holds at every tier); a primary residence tops out at 90% combined LTV (minimum credit 600), and its $750,000 maximum line is available only at 75% combined LTV or below with a 700-or-better credit profile (720 on the longer-runway program) and a full appraisal. Lines above $500,000 require a full appraisal. Credit, debt-to-income, property type, and full underwriting review all affect the final line.
Why There Is No Honest List of Banks
No neutral, reliable list exists of banks that write ADU lines, and the HELOCs they offer change by borrower, property, and lender appetite. Any list would therefore be stale or a sales pitch.
What you can know is the category of lender and what that category tends to do. A HELOC on your own home is a common product. A HELOC on a rental is not. NerdWallet says investment-property HELOCs are not offered by all lenders, that the lender pool is smaller, and that borrowing limits run lower than on a primary home. It adds that most lenders charge higher rates and fees on those lines. Some also restrict by location or by whether the home is rented year-round.
Lenders that keep loans on their own books, such as community banks and credit unions, set their own underwriting. That makes them a more likely source of rental-collateral lines than a lender selling its loans to investors. Some banks and credit unions also market ADU-specific lines, usually for owner-occupants.
A broker’s edge is breadth. One bank gives you one set of rules. A broker sees many lenders’ guidelines at once and can match the property, credit profile, and equity to the program that fits. The best program for your situation is the one whose limits match your file, not the one with the loudest advertising.
How a Build-Phase HELOC Works, Step by Step
A HELOC is a second-lien (or sometimes first-lien) revolving line. It is not a construction loan. The mechanics decide whether it suits an ADU, so walk through them in order.
Step 1: Pick the collateral. The line can sit on your primary home or on an existing rental where the ADU will be built. That choice drives which lenders are available and which limits apply.
Step 2: The lender sizes the line on current value. The lender takes today’s value, applies a combined-LTV ceiling, and subtracts your existing liens. The finished ADU’s value is not part of that math. Valuation-after-completion belongs to renovation and construction loans.
Step 3: Valuation and file review. On Lendmire’s network, lines at or below $500,000 ordinarily run an automated valuation with no traditional appraisal. A higher CLTV may require a secondary valuation. Every line above $500,000 needs a full appraisal, and you can request one in any case. Expect income and debt review, title review, and credit review as well.
Step 4: Draw. This is where an ADU build and a HELOC can clash. On Lendmire’s network, at least 75% of the line is drawn at closing. Interest-only payments therefore start on most of the line before the first contractor invoice is paid. On both network programs, pricing floats through the draw and repayment periods and never converts to fixed. Other lenders may structure this differently, so ask each one directly. After closing, the minimum subsequent draw is $1,000 on the structure that states one.
Step 5: Build and carry. The ADU produces no income. You carry the payment on your own income during construction and lease-up, so budget for that gap.
Step 6: Permit, finish, lease. Once the unit has its certificate of occupancy and a lease, an appraiser can prepare a rent schedule. Form 1007 covers a single-family rent schedule, and Form 1025 covers a small income property.
Step 7: Exit. Many owners refinance the HELOC balance into a longer-term loan. The DSCR route sizes that loan to the property’s rent roll.
What the Network’s Programs Allow
Lendmire brokers HELOCs through select wholesale partners and is never the lender. Every figure below is subject to lender guidelines and full file review, and none is a commitment to lend. Availability is limited to Lendmire’s 16 full-service states, which is narrower than its 41-market DSCR footprint, Washington, D.C. included.
Two draw structures exist on primary residences and second homes. The first is a 3-year interest-only draw followed by a 17-year repayment. The second is a 5-year draw followed by a 25-year repayment. Investment lines run the 5-year-draw structure only.
| Occupancy | Max CLTV | Credit | Max line |
|---|---|---|---|
| Primary residence | 90% (720+ only) | 600 floor | $500,000 at 90% CLTV; $750,000 at 75% CLTV, 700+ (720 on the longer-runway program) |
| Second home | 90% (720+ only) | 640 floor | $500,000 |
| Investment property | 70% | 700 floor | $500,000 |
Lower credit tiers step the ceiling down. On a primary residence, a 700 score reaches 85% CLTV up to $500,000 and 75% CLTV up to $750,000. The 90% tier exists only at 720 or better and only up to $500,000.
The $500,000 caps in the table apply to second homes and investment lines, and to primary-residence lines at the higher CLTV tiers. A line above $500,000 is for primary residences only. It needs a credit profile of 700 or better (720 on the longer-runway 5-year-draw structure), caps at 75% CLTV, and requires a full appraisal.
On Lendmire’s network, an investment line caps at 70% CLTV.
Other limits matter for an ADU plan:
- DTI: The maximum is 50%, or 45% for credit from 600 to 679. The lender reviews your file on the interest-only payment at the maximum draw.
- Exposure: A borrower is limited to three lines. An owner with more than 15 financed properties is not eligible.
- Property types: Single-family, 2-4 units, PUD, townhome, and condominium are eligible. Manufactured homes, log homes, co-ops, condotels, commercial, mixed-use, and agricultural zoning are not. Modular factory-built homes are eligible on only one of the two structures.
- Self-employed borrowers: They qualify on documented income under the applicable program, subject to lender guidelines.
Titling matters. The borrower must hold title individually or in a revocable living trust. LLCs, corporations, partnerships, and irrevocable, blind, or land trusts cannot hold title on these lines, subject to program terms. A rental already deeded to an LLC needs a vesting change, or a DSCR cash-out refinance is the better tool.
How Much Can You Actually Borrow?
You can borrow the gap between the CLTV ceiling and what you already owe, up to the line cap. The ADU’s future value adds nothing to the calculation.
Say you own a primary residence with a first mortgage equal to 50% of its value, and your credit profile supports 75% CLTV. That leaves room for a line equal to about 25% of the home’s value, up to the program’s line cap. On an investment property with a first mortgage at 55% of value, the 70% ceiling leaves room for a line of about 15% of value. The same structure at the same property value produces a much smaller line on a rental.
Recent buyers feel this hardest. A home bought with 20% down has little equity to tap until it appreciates or the first mortgage is paid down. If the line is smaller than the build, you have options. Final terms depend on lender guidelines, property type, leverage, and the borrower’s complete credit picture.
- Cover the gap with cash.
- Phase the project.
- Look at a renovation or construction loan that underwrites to after-completed value, which may fit larger detached builds.
- Wait and refinance once the unit is rented.
A few states apply their own combined-LTV caps on primary homes. Ask the lender whether one applies to your property.
HELOC, Home Equity Loan, Cash-Out, or Construction Loan?
The right tool depends on equity, project size, and what you want your first mortgage to do. A HELOC lets you keep your existing first mortgage in place. A cash-out refinance replaces the whole loan.
| Option | Sizing basis | Best fit |
|---|---|---|
| HELOC | Current value, CLTV cap | Moderate builds with real equity |
| Home equity loan | Current value, lump sum | Fixed budget, one draw |
| Cash-out refinance | Current value, new first loan | Replacing the first mortgage anyway |
| Construction or renovation loan | Completed value, staged draws | Thin equity, larger builds |
| DSCR refinance | Rent against payment | Stabilized, leased ADU |
For investors, the key distinction is timing. The first four options fund the build. The last one funds the stabilized property. Lendmire’s piece Best HELOC Program to Build a Granny Flat or ADU covers the owner-occupant side of the decision in more detail.
Investors and Rental Collateral
If you plan to rent the ADU, the collateral question comes first. Putting the line on your primary home uses your own residence to secure a rental improvement. That is a personal-risk tradeoff, and it keeps you in the widest part of the lender pool.
Putting the line on an existing rental keeps the risk on the investment. The product is narrower, though.
The rental-collateral line also adds a payment to the property’s debt load. Any balance you pay off in a later refinance rolls into the new loan, so size the refinance with the HELOC balance in mind.
NerdWallet’s companion guide on investment-property HELOCs points owners who primarily rent a property toward a DSCR second mortgage as a possible best option. That fits the sequence most investors follow anyway.
The Exit: Turning the Finished ADU Into a DSCR Loan
A DSCR loan is reviewed primarily on property-level rental income covering the payment, subject to lender guidelines. It is the natural exit once the ADU is rented. The complete DSCR loans guide walks through the full program.
Across Lendmire’s wholesale network, the typical numbers look like this:
- Cash-out refinance: On standard rentals it tops out around 75% LTV, and about 6 months of seasoning is the common expectation.
- Coverage: 1.00 is where many select programs start. A separate select-lender path goes below 1.00, with leverage and terms adjusted. Stronger coverage opens better pricing and leverage.
- Credit: Most programs want around 660. A 620 floor exists in parts of the network, and 700 or better unlocks the strongest leverage tiers.
- Loan size: Up to $3,000,000 on standard programs, with smaller balances available through select lenders.
The legality of the ADU decides whether its rent counts at all. Lenders generally require the unit to be permitted and finished, often with a certificate of occupancy. The appraiser may need ADU comparables before the rent holds up. Some programs want a separate rent schedule per rentable unit, and others accept a combined figure. Rent from an unpermitted unit is generally excluded.
For contrast, the Freddie Mac ADU fact sheet shows how appraisal-driven underwriting treats ADUs in the agency world. It requires at least one comparable sale with an ADU and at least one rented ADU among the rental comparables. It also says income from an illegal ADU may not be used to qualify. Those are agency rules, not DSCR rules, but they show the same gate: legality and comparables.
Classification matters too. A main house plus an ADU can be read as one unit with extra rent or as a two-unit property, and that changes the appraisal form. Short-term-rental use of an ADU adds documentation questions. Short-term rental rules can vary by city, county, HOA, and property type, so investors should confirm local rules before relying on projected rental income.
One more point. DSCR compares rent to the payment only. Clearing 1.00 is not the same as positive cash flow, because repairs, vacancy, management, utilities, and capex sit outside the calculation.
Where the General Rule Breaks
Most of this article assumes a standard build with real equity. A few situations bend the rules.
- Short draw windows. Some lines allow only a short draw period. If permitting delays push your schedule, the draw could end before construction does. Match the draw end date to the build plan.
- Use restrictions. Some lines can be used for construction only.
- LLC-titled rentals. As covered above, the title must change, or a DSCR cash-out replaces the HELOC idea.
- Manufactured or log structures. Manufactured homes, log homes, and barndominiums are not offered under the network’s DSCR programs. A prefab ADU needs a closer look at what it actually is.
- Foreclosure or bankruptcy history. A bankruptcy needs 4 years of seasoning from discharge or dismissal. Foreclosure history splits by program, with one structure seasoning it and the other declining it outright.
- Thin equity or a large detached build. The ADU’s finished value is the real source of funds in that case, which points toward a construction or renovation loan.
Honestly, the stronger play for an investor with thin equity is often to wait. Build equity first, or pair a smaller HELOC with cash. Borrowing on a primary home to fund a rental that does not yet exist is a bet on permits, construction costs, and tenants all going right.
Questions to Ask Before You Apply
Lenders differ on ADU details, so ask these directly:
1. Does the line allow draws for ground-up construction, or only renovation?
2. How much of the line is drawn at closing?
3. How long is the draw period, and what happens if the build runs past it?
4. Does the line float for the whole term, or can it convert to fixed?
5. Does the lender size the line on current value only?
6. What valuation does the lender require at my line size?
7. Can the line sit on a rental, and does the title need to change?
8. Is there a minimum draw after closing?
Have these ready before you apply:
- Zoning and permit feasibility for the lot.
- A contractor bid or design-build agreement.
- Your credit, income, and debt documents.
- A clear view of how the line will sit alongside your existing first mortgage.
A lot that cannot legally hold an ADU undermines the whole plan, and lenders do not want to fund a build that cannot be permitted.
Where to Start
If you are considering a home equity line and want to see how the numbers work, Lendmire can help you compare HELOC options based on the property, the equity available, credit profile, combined leverage, and your goals. You can reach the team at 828-256-2183 or request a quote through Lendmire’s quote page.
Frequently Asked Questions
Can you use a HELOC to build a granny flat or ADU?
Yes, if the lender allows the funds to go toward construction. A HELOC is revolving credit secured by your property, so you draw as costs arise. On Lendmire’s network, the line is sized on current value, and at least 75% is drawn at closing. Confirm that the lender permits ground-up construction, not just renovation.
Do banks offer a HELOC on a rental property to build an ADU?
Some do, but the pool is smaller than for primary homes. Investment-property HELOCs are not offered by all lenders and carry lower limits. On Lendmire’s network, an investment line needs at least a 700 score, caps at 70% CLTV, and tops out at $500,000. A broker can match your property to a lender whose program fits.
Will a lender count the ADU’s future rent or value?
Not at the HELOC stage. The line is sized on today’s value, and the ADU produces no income during construction. Rent generally counts toward the permanent loan only once the unit is permitted, finished, leased, and appraised. A finished improvement may support a higher appraised value, depending on comps and underwriter review.
Can an LLC borrow against the property?
No. On Lendmire’s network, title must be held by the individual borrower or a revocable living trust. LLCs, corporations, partnerships, and irrevocable, blind, or land trusts cannot hold title on these lines. A property already in an LLC needs a vesting change, or a DSCR cash-out refinance is the better route.
What happens to the HELOC after the ADU is built?
Many owners refinance the balance into a longer-term loan. A DSCR refinance sizes the loan to the property’s rent against its payment, subject to lender guidelines. The HELOC balance is paid off and rolled into the new loan, so plan the refinance with that balance in mind.
About Lendmire
Lendmire is a mortgage brokerage (NMLS# 2371349) arranging home equity lines of credit — primary-residence, second-home and investment-property lines — through a wholesale lending network in its 16 full-service states. Eligibility is determined by the lender on each file. Scotsman Guide named Lendmire a Top Mortgage Workplace in both 2025 and 2026.
Get Started
Ready to find the right loan for you?
See your offer in seconds. No credit pull, no obligation.
Informational only. Not a Loan Estimate, approval, or commitment to lend. Program availability and eligibility are subject to lender guidelines, credit approval, property review, and underwriting.
References
1. NerdWallet
2. NerdWallet – HELOC on an investment property (companion guide)
3. Freddie Mac – ADU fact sheet
This article is part of Lendmire’s HELOC & home equity loan program — full qualification details, guidelines, and scenarios live on the program page.
Related reading: Banks That Offer a DSCR HELOC on a Rental Using Only Cash Flow · Banks That Offer a DSCR HELOC on a Non-Warrantable Condo · Banks That Offer an Investment Property HELOC Without Your Spouse on the Loan
Brandon Miller
Founder & CEO, Mortgage Loan Originator, Lendmire LLC
- Mortgage Loan Originator · NMLS# 1129696 · Verify on NMLS Consumer Access
- North Carolina Real Estate Broker · License# 343312 · Verify on NCREC
- North Carolina Insurance Producer · License# 19053198 · Property, Casualty, Life, Health · Verify on NAIC SBS
- Lendmire LLC · Firm NMLS# 2371349 · Verify firm licensure
Disclosure information. Lendmire is a state-licensed mortgage brokerage under NMLS# 2371349. Lendmire is not a depository institution, direct lender, or financial advisor — all loans referenced are placed through wholesale lender partners and are subject to each lender's underwriting standards. This article is provided for general informational purposes and is not a commitment to lend, nor does it constitute financial, legal, or tax advice. Loan programs, terms, rates, and qualification standards change without notice and depend on borrower profile, property type, and the state in which the subject property is located. Equal Housing Opportunity provider. NMLS Consumer Access: nmlsconsumeraccess.org.