An accessory dwelling unit (ADU) can turn one rental into two income streams on the same lot. The hard part is paying for the build before the second unit earns anything.
The Quick Read: An investment property HELOC can fund an ADU when the rental carries enough equity, you hold title personally or in a revocable trust, and you accept that the line is sized on what the property is worth today, not on what the finished unit will be worth. Subject to lender guidelines, the key facts are:
- Investment lines in Lendmire’s wholesale network cap at 70% combined loan-to-value (CLTV), with a 700 minimum credit score and a $500,000 maximum line.
- Lines at or below $500,000 ordinarily use an automated valuation, so the unbuilt ADU adds nothing to the number.
- At least 75% of the line is drawn at closing. It then runs a 5-year interest-only draw followed by a 25-year fully amortizing repayment, and the pricing floats.
- LLCs cannot hold title on these lines, which is the sharpest difference from a DSCR loan.
- The usual exit is a DSCR cash-out refinance once the unit is permitted, finished and leased.
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 an Investment Property HELOC Actually Is
A home equity line of credit (HELOC) is a revolving credit line secured by property you own. Equity is the property’s value minus what you owe against it. The line is a second mortgage if a first mortgage already exists, or a first lien if the property is paid off.
On an investment property, the product gets narrower. Large retail lenders often decline rentals altogether. NerdWallet’s explainer on HELOCs for investment properties says not every lender offers them, qualification is strict, and lenders see higher default risk than on a primary home.
Lendmire brokers these lines through select wholesale partners. It is the broker, never the lender, and every figure here is subject to lender guidelines and full file review. The HELOC product is available only in a limited set of states, a narrower footprint than Lendmire’s DSCR investor lending across 41 markets, including Washington, D.C.
Which Property Should Secure the Line?
You have two real choices, and they carry very different risk. You can put the line on the rental where the ADU will sit, or on a home you live in and spend the money on the rental. The ceilings differ by occupancy, so match each figure to the property that secures the line.
| Factor | Line on the rental | Line on your primary home |
|---|---|---|
| Max CLTV | 70% | Up to 90%, only at 720+ credit |
| Minimum credit | 700 | Varies by program |
| Max line | $500,000 | Up to $750,000 |
| Collateral at risk | The rental | Your home |
The primary-home route offers more leverage, but you are pledging the house you sleep in to build a rental. Cost overruns and slow leasing then sit on your own home.
For a deeper look at choosing between programs, see Lendmire’s piece Best Investment Property HELOC Program for an Accessory Dwelling Unit.
How Underwriting Treats an ADU Build
Underwriting for a HELOC looks at you and at today’s property. It does not give credit for the unit you plan to build. This is the point that surprises most first-time ADU investors.
Researchers at the Terner Center at UC Berkeley found that very few owners could borrow against the expected value of an unbuilt ADU. In their survey, about 40% of respondents who borrowed used existing home equity. The survey is dated, but the lesson holds: you borrow against equity you already have.
Here is how a file moves through review on an investment line:
1. Equity. The lender takes the CLTV ceiling, applies it to current value, then subtracts existing liens. On an investment property that ceiling is 70%.
2. Valuation. Lines at or below $500,000 ordinarily use an automated valuation with no traditional appraisal. You may request a full appraisal in any case, but it will still value the property as it stands.
3. Credit. An investment line needs at least a 700 score. Credit above 700 buys eligibility rather than extra leverage, because 720 and 700 reach the same 70% ceiling.
4. Debt-to-income (DTI). The maximum is 50%. The lender reviews your file on the interest-only payment calculated on the maximum draw, so a large line weighs on the ratio from day one.
5. Title. The borrower must be an individual or an inter vivos revocable living trust. This is the quiet deal-breaker for investors who hold rentals in LLCs.
The Timing Problem: Build, Permit, Lease
The ADU earns no rent until three things happen: it gets built, it passes inspection, and a tenant moves in. The line starts costing money at closing.
That sequence creates a gap. You carry the full interest-only cost on the drawn balance while the unit produces nothing. Plan the gap as a real budget line, and fund it from reserves rather than from the property’s existing rent.
The structure makes this sharper. At least 75% of the line is drawn at closing, so this product behaves less like a pay-as-you-build construction line. After closing, minimum subsequent draws are $1,000 on the program that states one. A line that is mostly drawn on day one starts costing interest on the whole balance well before the first contractor invoice.
The Consumer Financial Protection Bureau (CFPB) describes the general HELOC design as a draw period during which you borrow up to the limit. It also warns that a significant drop in the home’s value can lead a lender to stop further draws.
How to Use an Investment Property HELOC for an ADU, Step by Step
1. Confirm the unit is legal and rentable. Local ADU rules decide whether you can build and lease it. Check zoning, permits and any owner-occupancy conditions before you borrow.
2. Check title. If the rental sits in an LLC, a corporation, a partnership or an irrevocable, blind or land trust, the property cannot secure these lines as titled. A vesting change or a different loan type is needed first.
3. Price the equity. Take 70% of current value on an investment property, subtract existing liens, and compare the result to the $500,000 cap. The smaller number wins.
4. Size the build to the line, with a buffer. Because most of the line is drawn at closing, the undrawn portion is small. Overruns usually come from your own cash.
5. Check the property type. Single-family homes, 2-4 unit properties, PUDs, townhomes and condominiums, including non-warrantable condos, are eligible. Manufactured homes, co-ops, condotels, log homes, commercial, mixed-use and agriculturally zoned properties are not.
6. Count your lines. A borrower is limited to three lines in total, and an owner of more than 15 financed properties is not eligible.
7. Build, permit, lease. Keep invoices and permit records organized. You need them to prove the unit exists when you refinance.
8. Plan the exit before you close. The line floats and amortizes on a schedule, so it works as a bridge. The next section covers the takeout.
If you plan to run the unit as a 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.
A Worked Example in Percentages
Run the numbers using modeled assumptions only, with no dollar amounts. Suppose a single-family rental has an automated value that sets 100% as the baseline.
Scenario one: a paid-off rental. The line sits in first position and reaches up to 70% of value, subject to the $500,000 cap. At least 75% of that line is drawn at closing, or about 52% of value. Equity is rarely the limit here; the cap and your DTI more often are.
Scenario two: an existing first mortgage at 45% of value. At the 70% ceiling, the new line can reach about 25% of value in second position. Drawing 75% at closing means about 19% of value goes out the door on day one. If the build budget is larger than that, the HELOC alone does not cover it.
Scenario three: slow lease-up. The unit finishes, but the first tenant arrives months late. The interest-only cost keeps running on a mostly drawn balance, and the pricing floats with the market. A file that works with the unit leased may feel tight during the vacant stretch, so keep reserves for it.
Scenario four: cost overrun. The line is already largely drawn, so the extra cost comes from your own cash. If you cannot absorb a meaningful overrun, borrow less or wait.
A practical note on scale: the HELOC is the right size when the build budget fits inside the equity at 70%, with room left over for the vacancy gap.
Where the General Rule Breaks
The general rule is that the line is sized on today’s value and secured by your personal title. Several situations break it.
- LLC-held rentals. These lines cannot close on LLC title. A DSCR loan commonly allows LLC vesting, subject to lender program eligibility. A property already deeded to an LLC needs a vesting change or a DSCR cash-out instead.
- Thin equity or a large detached build. If the numbers do not reach, a construction or renovation loan sized on completed value fits better. Few HELOC programs lend against a unit that does not exist.
- Listed or recently listed property. A property listed for sale, or listed within the past 60 days, is ineligible in some states where the line is offered.
- Ineligible property types. Manufactured homes, log homes and barndominiums are not offered, on these lines or on the network’s DSCR programs.
- Second-lien position. The product allows a first or second lien, but a larger existing mortgage shrinks the room under the 70% ceiling.
- Mixed or agricultural zoning. Mixed-use and agriculturally zoned properties are not eligible, even if the ADU would be residential.
- Classification after the build. A single-family home with an ADU may be treated as a one-unit property with an accessory unit or as a two-unit. Which applies depends on the program and the appraisal.
HELOC Versus the Alternatives
The best product depends on equity, timing and how you hold title.
| Option | Best for | Main trade-off |
|---|---|---|
| Investment HELOC | Rental with equity, personal title | 70% cap, floating cost |
| Primary-home HELOC | High equity in your own home | Your home is the collateral |
| DSCR cash-out refinance | Leased, seasoned rental | Needs rent evidence first |
| Construction loan | Thin equity, large build | Different underwriting |
A DSCR cash-out refinance is a poor fit before the unit exists, because the property has no new rent to point to. It becomes the strongest tool afterward.
The Exit: Refinancing into a DSCR Loan
Once the ADU is permitted, finished and leased, the property has rent evidence. A DSCR cash-out refinance can then pay off the HELOC. A DSCR loan is reviewed primarily on property-level rental income covering the payment, subject to lender guidelines, instead of your personal DTI.
Here is how the takeout typically looks across the network:
- Leverage. A cash-out refinance on a standard rental tops out around 75% LTV across most of the network.
- Seasoning. About six months of ownership or title history is the common expectation.
- Coverage. 1.00 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. A 620 floor exists in parts of the network, most programs want around 660, and 700 or higher unlocks the strongest leverage tiers.
- Reserves. These vary by lender, leverage, loan size and transaction type, and are commonly around six months of PITIA (principal, interest, taxes, insurance and any HOA dues).
- Structure. The spine is the 30-year fixed. Extended terms and interest-only periods are available through select lenders in the network.
A DSCR loan compares rent to PITIA only. Clearing 1.00 does not mean positive cash flow. Repairs, vacancy, management, utilities and capital expenses sit outside that calculation.
Many investors treat the HELOC as the construction bridge and the DSCR loan as the permanent home. To see how the pieces fit, read Lendmire’s guide How to Use a DSCR HELOC for an Accessory Dwelling Unit. For the full picture of how DSCR financing works, see the complete DSCR loans guide.
Key Terms Defined
ADU (accessory dwelling unit): A second, self-contained living space on the same lot as a main home, such as a garage conversion, an attached unit or a detached cottage.
CLTV (combined loan-to-value): All loans secured by the property, added together and divided by its value.
Draw period: The stretch when you can borrow from the line. The CFPB’s HELOC booklet describes the line as revolving credit with the home as collateral and variable pricing.
Interest-only payment: A payment covering only the interest on the balance, with no principal reduction.
DSCR (debt service coverage ratio): Monthly rent divided by the monthly PITIA. A result of 1.20x means rent is 120% of the payment.
Seasoning: The waiting period a lender wants before you can refinance a property.
Pre-Borrowing Checklist
- Confirm local rules allow you to build and rent the unit.
- Confirm title is personal or a revocable living trust.
- Calculate equity at 70% CLTV and compare it to the $500,000 cap.
- Check that your credit profile meets the 700 minimum.
- Budget interest through the full build and a vacant lease-up period.
- Keep cash outside the line for overruns.
- Keep a clear record of permits, invoices and the lease for the refinance.
Frequently Asked Questions
Can I use a HELOC on a rental held in an LLC?
Not on these lines. Title must sit with an individual borrower or an inter vivos revocable living trust. LLCs, corporations, partnerships and irrevocable, blind or land trusts cannot hold title. If the property is already in an LLC, you would need to change vesting or use a DSCR cash-out refinance instead.
Does the future rent from the ADU count toward qualifying for the line?
No. Underwriting looks at your credit, your DTI and the property’s equity today. The line is qualified on the interest-only payment calculated on the maximum draw. Rent from the finished unit becomes relevant later, when a DSCR loan takes out the line.
Can I use my primary home’s equity to build an ADU on a rental?
Yes, because a primary-residence line has no requirement that the funds go to that home. The ceiling on a primary-residence line reaches 90% CLTV, and only at a 720 or better credit profile. The trade-off is that your own home secures the debt.
Will the HELOC cover the entire cost of the build?
Often not. An investment line caps at 70% CLTV and $500,000, and an existing mortgage reduces the room. At least 75% of the line is drawn at closing, so you can end up with funds ahead of the work and little room for overruns. Plan to cover a buffer with cash.
Do I have to refinance when the ADU is finished?
No rule forces it, but many investors do. The line carries a 5-year interest-only draw and a 25-year repayment, with pricing that floats and never converts to fixed. A DSCR cash-out refinance can replace it with a fixed structure once the unit is leased and the property has seasoned.
A Next Step
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.
About Lendmire
Lendmire (NMLS# 2371349) is a mortgage brokerage serving homeowners and real estate investors in its 16 full-service states. Home equity lines of credit are arranged through wholesale lending channels; Lendmire brokers the line and the lender underwrites each application under its occupancy-based 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. NerdWallet’s explainer on HELOCs for investment properties
2. Terner Center at UC Berkeley – Jumpstarting the Market for ADUs
3. Consumer Financial Protection Bureau (CFPB)
This article is part of Lendmire’s investment property HELOC program — full qualification details, guidelines, and scenarios live on the program page.
Related reading: Can You Get an Investment Property HELOC After a Denial on Returns? · Can You Get an Investment Property HELOC When Speed and Convenience Matter Most? · Can You Get an Investment Property HELOC With One Unit Vacant?
Brandon Miller
Founder & CEO, Mortgage Loan Originator, Lendmire LLC
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Legal disclosures. Lendmire (NMLS# 2371349) is a state-licensed mortgage brokerage that arranges financing through wholesale lender relationships. Lendmire is not a direct lender, depository institution, or registered financial advisor. The discussion above is general informational content about real estate financing — it is not financial, legal, or tax advice, and readers should consult licensed professionals for guidance on their individual circumstances. Loan inquiries are subject to lender underwriting; this article does not represent a commitment to lend. Loan terms, rates, and qualification standards vary by borrower, property, and state, and are subject to change at any time. Equal Housing Opportunity. NMLS Consumer Access: nmlsconsumeraccess.org.