How an Investment Property HELOC Works for an Accessory Dwelling Unit

The Quick Read: A home equity line of credit (HELOC) on a rental you own lets you borrow against its equity and draw the money to build an accessory dwelling unit (ADU). The lender sizes the line on the property as it stands today, so the unbuilt unit’s future value and rent do not count toward the amount.

• On an investment property, the ceiling across Lendmire’s wholesale network is 70% combined loan-to-value (CLTV), meaning every loan on the property added up against its value. The minimum credit score is 700, and the line tops out at $500,000.
• At least 75% of the line is drawn at closing, so interest starts on most of the money before the ADU earns a dollar.
• Pricing floats for the life of the line and never converts to fixed.
• Title must sit in your own name or a revocable living trust. LLCs cannot hold title.
• If the finished unit’s rent has to carry the financing, a DSCR cash-out refinance after the build is the usual second step.

What Is an Investment Property HELOC?

An investment property HELOC is a revolving credit line secured by a rental you own. It works like a home equity line on a primary residence, with tighter limits. Lendmire is a broker, so it arranges these lines through select wholesale partners. Every figure below is subject to lender guidelines and full file review, and none is a commitment to lend.

The line can sit in first or second lien position. A second lien sits behind your existing mortgage. With no mortgage on the rental, the line becomes the only lien, and your full equity is the starting point for sizing.

An ADU is a small, legal second dwelling on the same lot or inside the same building. Think of a detached backyard cottage, a garage conversion, or a basement apartment. The lender cares about two things: what the property is worth today, and whether you can carry the debt while the unit earns nothing.

How Does the Line Work From Closing to Payoff?

The line has two phases: a five-year interest-only draw period, then a 25-year repayment period. On an investment property, this is the only structure on the network. Your payment during the draw covers interest on what you have drawn. After that, payments include principal and run on a fully amortizing schedule.

Two features surprise most investors.

First, at least 75% of the line is drawn at closing. You start paying interest on most of the line right away, so size the line to the build rather than to your maximum equity.

Second, pricing floats across both phases. Payments can change when pricing moves, and they can step up when the draw period ends. The CFPB’s HELOC booklet lays out the same basic structure, with variable pricing, a draw period, and a repayment phase. It is an older consumer document, so use it for structure and not for current terms.

How Much Can You Actually Borrow?

You can borrow up to 70% CLTV, capped at $500,000. The same ceiling applies at 700 and at 720 or better. Credit above 700 buys eligibility, not extra leverage, and 700 is a hard floor with no tier beneath it.

Here is the arithmetic in percentages. Say your rental is paid off. The full 70% of its current value is available, up to the cap. Say your first mortgage already equals 50% of value. Then the line can add roughly 20 more points of value, and no more.

Primary residences follow a different table. On a primary residence, the ceiling reaches 90% CLTV, and only at a 720-or-better credit profile. If you hold the line on your home to fund an ADU on your rental, that table applies to your home. It does not apply to the rental.

Then the lender checks your debt load. Maximum debt-to-income (DTI) is 50%, and the lender reviews your file on the interest-only payment calculated as if the full line were drawn. That is a stricter test than your actual early payment.

Does the ADU’s Rent or Future Value Count?

No. On a standard HELOC, neither one counts before the unit exists. A line of $500,000 or less ordinarily uses an automated valuation instead of a traditional appraisal. That makes it almost always a valuation of the property as it is now. You can request a full appraisal in any case, but it will still value the rental as it stands.

Terner Center research on ADU financing points the same way. Its California work found that most ADU owners used cash plus a mortgage, and that home equity loans and cash-out refinances were the most common mortgage types. It also recommends that lenders consider ADU rental income in underwriting and change how ADUs are appraised. A recommendation like that tells you these changes are not standard practice.

Rental income does matter later, on a different loan. A DSCR loan compares the property’s rent to its full monthly payment (principal, interest, taxes, insurance, and any HOA dues). That test needs a lease or a market-rent appraisal on a finished, rentable unit. Clearing the test also does not mean positive cash flow. Repairs, vacancy, management, utilities, and capital costs sit outside the calculation.

Which Property Secures the Line?

Two setups look similar and behave very differently.

Either way, the lender looks at the collateral’s current condition, your credit, and your debt load. The ADU is a use of funds, not a source of qualifying income. Lenders still expect the unit to be legally permitted. Local authorities decide whether it may be built, and the lender decides whether you qualify. One approval does not produce the other.

Where Does the General Rule Break?

Several edge cases change the answer.

LLC-held rentals. Title must be held by you personally or by a revocable living trust. LLCs, corporations, partnerships, and irrevocable, blind, or land trusts cannot hold title. That is the sharpest structural difference from a DSCR loan, which can close in an LLC, subject to program eligibility. A rental already deeded to an LLC needs a vesting change, or a DSCR cash-out refinance instead.

Property type. The line covers single-family homes, 2-4 units, PUDs, townhomes, and condos, including non-warrantable condos. Manufactured homes, co-ops, condotels, log homes, commercial, mixed-use, and agricultural-zoned properties are not offered.

Portfolio limits. A borrower is limited to three lines in total. Owning more than 15 financed properties makes you ineligible.

Credit history. The lender pulls a single-bureau score tied to the primary wage earner, and the report cannot be more than 90 days old at closing. A bankruptcy needs four years of seasoning from discharge or dismissal. Foreclosure history on an investment file follows a seven-year path, with four years for a deed-in-lieu, pre-foreclosure, or short sale.

Large builds. A line above $500,000 is for primary residences only. It requires a full appraisal and a credit profile of 700 or better (720 on the longer-runway structure). An investment line cannot reach that size. A build that needs more than $500,000 usually moves to a different financing path.

Availability. These lines are offered only where Lendmire is a full-service mortgage brokerage: 16 states. That footprint is narrower than its DSCR footprint of 41 markets, including Washington, D.C.

Key Terms Defined

HELOC: A revolving credit line secured by a property, with a draw period followed by a repayment period.

ADU: A legal secondary dwelling on the same lot or in the same building as the main home.

CLTV: Combined loan-to-value, which is every loan against the property divided by its value.

Draw period: The stretch when you can borrow from the line and pay interest only.

Lien position: Your place in line for repayment if the property is sold. First lien is paid before second lien.

DSCR: Debt service coverage ratio, which compares a rental’s income to its full monthly obligation.

Seasoning: The waiting period a lender wants between buying or refinancing and your next transaction.

How Should You Choose a Route?

A HELOC and a DSCR cash-out refinance answer different questions. The HELOC keeps your first mortgage in place and is reviewed around credit and debt load. The DSCR cash-out replaces the first mortgage and qualifies primarily on property-level rental income covering the payment, subject to lender guidelines.

DSCR cash-out refinances on standard rentals top out around 75% LTV across most of the network, and about six months of seasoning is the common expectation. A coverage of 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. Every figure here varies by lender and program, and guidelines, property type, leverage, and credit profile all apply.

Short-term rental use is a separate category. Cash-out on short-term rental collateral tops out at 70%, with expectations of 12 months of hosting history.

What Does the Build-Then-Refinance Path Look Like?

Many investors treat the HELOC as the construction money and the DSCR cash-out as the long-term loan. The sequence runs in four steps. You draw on the line and build. You lease the finished unit. You document the new rent with a lease or a market-rent appraisal. Then you refinance if replacing the HELOC with fixed-structure debt makes sense.

A rent-based loan will not fund raw construction. It needs a finished unit with a lease or market-rent evidence, and it comes after the build. Appraisers also often fail to credit a new ADU’s rent right away, so a refinance may not return every dollar you spent.

What Can Go Wrong?

Run these stress tests before you sign.

• Cost overruns. An overrun draws on the same equity that secures your rental. With most of the line already drawn at closing, you have little cushion.
• Payment shock. Payments step up when the draw period ends and principal begins. Test that payment against the ADU’s eventual rent, and against the whole property’s finances if the unit sits vacant.
• Zero income during construction. The ADU earns nothing until it is finished and leased. Reserves should carry the line through that gap.
• Unpermitted or non-rentable units. A unit that cannot be legally rented has no rent to refinance on.
• Value that lags cost. Appraisals often credit an ADU less than it cost to build. Any improvement may support a higher appraised value, depending on comps and underwriter review.

For two related paths, see Lendmire’s piece on the best investment property HELOC program for an accessory dwelling unit. For a variation where you live in one unit of a multifamily, see how to qualify for an investment-property HELOC on a fourplex when you live in one unit. The complete DSCR loans guide covers the refinance side in more depth.

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. An editable, illustrative calculator on the site can give you a rough estimate before you talk to anyone.

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.

References

1. CFPB, HELOC consumer booklet

2. Terner Center, ADU Construction Financing