The Quick Read: It makes sense only when you hold real equity today, can carry a floating interest-only payment through construction, and have a plan to refinance into a DSCR loan once the unit is built and rented, because an investment property line is sized on what the property is worth now, not on the finished ADU. Through Lendmire’s wholesale network, an investment line caps at 70% combined loan-to-value, so it works as a short build bridge, not a permanent loan.
- Projected ADU rent does not help you qualify.
- Investment lines through the network require a 700 minimum credit score and top out at a $500,000 line.
- A DSCR loan generally cannot pay for raw construction. It is the exit once the unit is leased.
An accessory dwelling unit (ADU) is a second, smaller living unit on the same lot as a main home: a backyard cottage, a garage conversion, a basement apartment. Investors like them because they add rent without buying another property. The harder question is how to pay for one when the money has to come before the rent does. A home equity line of credit (HELOC) on the rental is one answer. Here is where it works and where it breaks.
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.
What Does a HELOC on a Rental Actually Do for an ADU Build?
It turns equity you already own into a pool of cash you can pull from during construction. That is all. It does not count the ADU’s value, and it does not count the ADU’s future rent.
A HELOC is a revolving line secured by your property. In this network it sits as a standalone first or second lien, which means it can sit behind your existing mortgage without replacing it. That matters if your current first mortgage is one you want to keep.
The lender sizes the line off what the property is worth today, then subtracts what you already owe. The finished ADU is not in that math. Think of it this way: you are borrowing against the house you have to build the house you want.
Investment property lines are also the narrow end of the HELOC market. They are harder to find and more conservative than lines on a home you live in. That is a feature of how the product is built, not a quirk of one lender, and it shapes everything below.
What Are the Limits on an Investment Property Line?
On an investment property, the network’s ceiling is 70% CLTV, with a 700 minimum credit score and a maximum line of $500,000. CLTV means combined loan-to-value: your first mortgage and the new line added together, divided by the property’s value.
Notice what the credit tiers do. Both 720-plus and 700-plus reach the same 70% ceiling on an investment line. A higher score above 700 buys you nothing extra in leverage. And 700 is a hard floor, with no tier beneath it.
Other terms that matter for an ADU build, all subject to lender guidelines and full file review:
- Structure. Investment lines run a 5-year interest-only draw period, then a 25-year fully amortizing repayment period. Pricing floats the whole way and never converts to fixed.
- Draw at closing. At least 75% of the line is drawn at closing. You cannot hold most of it in reserve and pull it as contractor invoices arrive.
- Line size. Lines run from $25,000 to $750,000 in general, but anything above $500,000 is for primary residences only.
- Debt-to-income. The maximum is 50%, and the lender reviews your file on the interest-only payment calculated on the full line.
- Valuation. At $500,000 or below, the line ordinarily runs on an automated valuation, often with no traditional appraisal. A higher CLTV can trigger a second valuation, and you can request a full appraisal in any case.
- Property types. Single-family, 2-4 units, PUDs, townhomes, and condos (including non-warrantable) are eligible. Manufactured homes, co-ops, condotels, log homes, commercial, mixed-use, and agricultural zoning are not.
- Exposure. A borrower is limited to three lines, and anyone owning more than 15 financed properties is not eligible.
Lendmire arranges these lines only in the states where it is a full-service mortgage broker.
The Title Problem
Here is the sharpest difference from a DSCR loan. The line must be held by you personally or by a revocable living trust. LLCs, corporations, partnerships, and irrevocable, blind, or land trusts cannot hold title.
If your rental is already deeded to an LLC, you have two choices: change the vesting before applying, or skip the HELOC and use a DSCR cash-out instead. Changing title has its own costs and consequences, so think it through before you do it.
Why Doesn’t the ADU’s Rent Count?
Because it does not exist. A HELOC underwriter looks at your credit, your debt-to-income ratio, and the equity in a property that is standing today. A lease that has not been signed proves nothing.
Investors know DSCR loans qualify on rent, so they assume rent projections can help a line too. They cannot, at least not in this network. The line qualifies you as a borrower, and the property supplies the equity.
It also means the value gap is yours to carry. A finished ADU may support a higher appraised value, depending on comps and underwriter review. It may also appraise for less than it cost to build. Plan the budget assuming the appraisal could disappoint you.
Local rules decide whether the unit can be rented at all. Permits, owner-occupancy requirements, and size limits differ widely by jurisdiction. If you plan to use it as a short-term rental, 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.
What Happens During the Draw Period and After?
During the draw period you pay interest only, on a floating payment. After it ends, the line becomes a fully amortizing loan, and the payment steps up because principal is now included.
The CFPB’s explainer on home equity lines describes the same shape. Payments are often significantly higher once repayment starts. It also warns that in some plans the whole balance can come due when repayment begins. That balloon risk is a feature of some plans, so read the terms of any line you are offered.
Two more points from the CFPB’s HELOC booklet matter to ADU builders:
- Payments can change even when you draw nothing more, because the pricing floats.
- If you sell the property, you are generally required to pay the line off in full.
Now put that next to the 75% draw at closing. If you build for several months, you pay floating interest on most of the line before the first contractor invoice is paid. You also pay it through the lease-up, the stretch between finishing the unit and getting a tenant in it. A vacant ADU with a floating payment and no rent is the scenario to stress-test before you sign.
A fixed payment would be easier to plan around. This product does not offer one.
Where Does a DSCR Loan Fit?
A DSCR loan is the exit, not the build loan. DSCR stands for debt service coverage ratio: the property’s monthly rent divided by its monthly mortgage obligation (principal, interest, taxes, insurance, and any HOA dues). A DSCR loan is reviewed primarily on property-level rental income covering the payment, subject to lender guidelines. It needs a rentable property at closing, which is why it cannot fund raw construction.
The usual sequence has three steps:
1. Fund the build with equity, using the line.
2. Finish the unit, get the certificate of occupancy, and lease it.
3. Refinance with a DSCR cash-out, which pays off the line and any first mortgage together.
Most files in the network’s cash-out lane top out around 75% LTV on a standard rental, and about six months of seasoning is the common expectation. Coverage thresholds vary by program. A 1.00 ratio is where many select programs start. A separate select-lender path takes coverage below 1.00, with leverage and terms adjusted. Stronger ratios open better pricing and leverage. Credit matters too: a 620 floor exists in parts of the network, most programs want around 660, and 700-plus unlocks the strongest leverage tiers.
Two cautions. First, clearing 1.00 does not mean the property cash flows. Coverage compares rent to the payment only. Repairs, vacancy, management, utilities, and capital expenses sit outside the calculation. Second, the refinance is sized on the new value. If the ADU appraised below its cost, the new loan may not repay the line in full, and you would bring cash to close the gap.
If you own the property in an LLC, a DSCR loan may still be available, subject to lender program eligibility. For the full picture of how these loans qualify, see Lendmire’s complete DSCR loans guide.
Which Route Fits Which Situation?
The right tool depends on which property holds the equity, whether a first mortgage is worth keeping, and whether the unit is already leased. This table shows the common fits.
| Your situation | Likely best route |
|---|---|
| Rental with equity, ADU not yet built | Investment line, then DSCR exit |
| Equity is in your own home, not the rental | Primary-residence line |
| Rental owned by an LLC | DSCR cash-out, or change title first |
| ADU already built and leased | DSCR refinance or cash-out |
| Thin equity or tight budget | Wait, or reduce scope |
A primary-residence line is a different product from an investment line. Its ceiling reaches 90% CLTV, but only at a 720-or-better credit profile. It also offers two draw structures: 3 years interest-only with 17 years of repayment, or 5 years interest-only with 25 years of repayment. If your own home has the equity and the ADU sits on it, that route often has far more room than the investment line does.
How the two routes compare:
| Factor | Investment line | Primary-residence line |
|---|---|---|
| Max CLTV | 70% | Up to 90% at 720+ |
| Minimum credit | 700 | 600 floor |
| Max line | $500,000 | Up to $750,000 |
| Draw structure | 5-year draw, 25-year repay | 3/17 or 5/25 |
Which property secures the loan is a structural choice with consequences for risk. A line secured by your home puts your home behind the build.
When Does It Make Sense, and When Should You Skip It?
It makes sense when most of these are true:
- You have real equity, and your first mortgage leaves room under a 70% combined ceiling.
- Your credit profile is at 700 or better.
- The build budget is firm, with a contingency, and a contractor has priced the work.
- The ADU is clearly legal and rentable where the property sits.
- You can carry the floating interest-only payment through construction and a vacant lease-up.
- You have a DSCR refinance or cash-out in mind as the exit.
Skip it, or look elsewhere, when any of these apply:
- Thin equity. If the first mortgage already uses most of the 70%, there is little left to draw.
- Uncertain rentability. Permits, local rules, or short-term rental limits could stop the unit from producing the rent you expect.
- Payment shock. If a higher payment at repayment would strain you, a floating line is a poor fit.
- A better use of the money. Some investors compare the ADU against putting the same capital toward another rental. That comparison is worth running before you commit.
- Title in an LLC. The line cannot close without a vesting change.
An overrun deserves its own word. The line is secured by the same property that holds your equity, so a cost overrun puts that property at stake. If costs run over, you either fund the difference from cash or reduce the scope.
A Worked Scenario in Percentages
Say you own a duplex in an investment-eligible property type, and your first mortgage sits near 50% of the current value. A 70% CLTV ceiling leaves roughly 20 points of value for the line. The $500,000 maximum caps it as well.
You draw at least 75% at closing, so interest-only payments start on most of the line right away. The build runs through permitting, construction, and final inspection. You then list the unit and find a tenant.
Now run the exit. The appraiser values the property with the finished ADU. If the new value supports a refinance at around 75% LTV, the DSCR cash-out may pay off the first mortgage and the line, and the rent on both units counts toward coverage. If the ADU appraised below its cost, the 75% ceiling applies to a smaller number, and the payoff may fall short. That gap is the real risk in the strategy. The exact numbers vary by lender and program and follow a full review of property, leverage, and credit.
Coverage works the same way in either case. A DSCR file clears when rent comfortably covers the full monthly obligation. A unit that rents well may take a file from borderline to comfortable. A unit that sits vacant leaves you carrying the line with no rent behind it.
Key Terms Defined
ADU (accessory dwelling unit): A second, smaller living unit on the same lot as a main property, such as a cottage, garage conversion, or basement apartment.
HELOC (home equity line of credit): A revolving line secured by the equity in a property, drawn in pieces and paid as you go.
CLTV (combined loan-to-value): All loans secured by the property, added together, divided by the property’s value.
DSCR (debt service coverage ratio): Monthly rent divided by the full monthly mortgage obligation, used to qualify rental properties.
Draw period: The stretch when you can borrow from the line, usually with interest-only payments.
Lease-up: The period between finishing a unit and getting a paying tenant in it.
Seasoning: The waiting period a lender wants between events, such as owning a property before a cash-out refinance.
What Should You Gather Before You Apply?
Have these ready:
- A current mortgage statement showing the first-lien balance
- Proof of how the property is titled (individual or revocable trust)
- Credit and debt information, since the line qualifies you personally
- A contractor bid with a line-item budget and a contingency
- Permit status and local ADU rules for the property
- Insurance information for the existing property
Confirm the title and the first-lien balance first. Those two items settle whether the route is open at all.
Frequently Asked Questions
Can you get a HELOC on an investment property at all?
Yes, but through fewer lenders and on narrower terms than a home you live in. Eligibility depends on lender guidelines, the property, and a full file review.
Does the ADU’s projected rent count toward qualifying?
No. The line is reviewed against credit, your debt-to-income ratio, and the equity in the property as it stands today. A unit that has not been built produces no rent. The rent matters later, when a DSCR refinance looks at what the finished, leased unit earns.
Can a DSCR loan pay for the ADU construction?
Generally not. A DSCR loan needs a rentable property at closing and qualifies primarily on property-level rental income covering the payment. It works as the exit after the unit is finished and leased, replacing the line with a longer-term loan, subject to lender guidelines.
What if the ADU costs more than I planned?
You cover the overrun from cash or reduce the scope, because the line is capped by your equity and the 70% ceiling. Build in a contingency before borrowing.
Can I use a HELOC on my own home to build an ADU I will rent?
Often, yes. Primary-residence lines reach higher CLTV, up to 90% at a 720-or-better credit profile, and they offer more line size. The ADU sits on the property that secures the loan. Weigh the risk of putting your own home behind a rental project before choosing this route.
Next Steps
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. Lendmire is a broker that arranges financing through select lenders in its wholesale network, and every figure above is subject to lender guidelines. It is not a commitment to lend. An illustrative calculator on the site can help you test combined leverage before you apply.
About Lendmire
Lendmire, NMLS# 2371349, is a mortgage brokerage that arranges home equity lines of credit through wholesale lending partners in its 16 full-service states. Lines on primary residences, second homes and investment properties are each reviewed individually by the lender under the program’s occupancy, credit and combined-loan-to-value guidelines. Scotsman Guide named Lendmire a Top Mortgage Workplace in both 2025 and 2026.
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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. CFPB’s explainer on home equity lines
This article is part of Lendmire’s investment property HELOC program — full qualification details, guidelines, and scenarios live on the program page.
Related reading: Investment Property HELOC Requirements for Combined Leverage on a Rental · Does a DSCR HELOC Make Sense for Home Improvements Instead of a Renovation Loan? · Investment Property HELOC Requirements and Timeline for Landlords
Brandon Miller
Founder & CEO, Mortgage Loan Originator, Lendmire LLC
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Disclosures. The information presented in this article is general market commentary, not financial, legal, or tax advice. Lendmire is a mortgage brokerage (NMLS# 2371349) — not a direct lender or depository institution — and loan placement is subject to lender underwriting. Nothing in this content represents a commitment to lend. Loan terms, pricing, and program availability vary based on borrower qualifications, property characteristics, and state of subject property, and are subject to change at any time. Lendmire complies with Equal Housing Opportunity requirements. Consumer access: nmlsconsumeraccess.org.