The Quick Read: A home equity line of credit (HELOC) can pay for an accessory dwelling unit (ADU) in phases. The line is sized on what your property is worth today, not on the finished unit. On the wholesale network Lendmire places these files with, most of the line is drawn at closing, so staging takes planning.
- The line is sized on current value and combined leverage. The ADU’s future value does not count.
- On an investment property, the network ceiling is 70% combined loan-to-value (CLTV), with a 700 minimum credit score and a $500,000 maximum line.
- At least 75% of the line is drawn at closing, which changes how “draw as you build” works.
- The draw period ends on a fixed date whether or not the unit is leased.
- A DSCR cash-out refinance is a common exit when the property qualifies as an investment rental.
What Does Staged Funding Mean for an ADU Build?
Staged funding means you pay for each phase of construction as you reach it, instead of funding the whole budget on day one. An ADU build moves in steps: design and permits, site work and foundation, framing and rough-ins, then finishes and final inspection. Each step has its own invoice.
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.
A HELOC fits that rhythm in theory. You borrow against equity, use the money in pieces, and pay interest only on what you have drawn. The idea is simple. The details decide whether it works.
Here is a planning split for a typical detached or garage-conversion build. These shares are modeled assumptions for illustration, not market data. Your contractor’s bid sets the real numbers.
| Phase | Pays for | Draw trigger | Share of budget |
|---|---|---|---|
| 1. Soft costs | Design, engineering, permits | Permit issued | About 10% |
| 2. Site and foundation | Excavation, utilities, slab | Foundation inspection | About 20% |
| 3. Frame and rough-ins | Framing, roof, plumbing, electrical | Rough-in inspection | About 30% |
| 4. Finishes | Drywall, fixtures, flooring | Punch list done | About 30% |
| 5. Contingency | Overruns, change orders | Only if needed | About 10% |
Read the running total as 10%, 30%, 60%, 90%, then 100% if the contingency gets used. Always build the contingency line into the budget. Few ADU projects finish exactly on the first bid.
Plenty of homeowners finance this way. A survey analysis from the Urban Institute found that 43% of homeowners used mortgage products to finance their ADU, and 56% of those used a HELOC or home equity loan. That is California-based data, not a national figure. Nationally, ADUs are still rare, at about 1.3% of homes in the same analysis.
The Catch on This Network: Most of the Line Draws at Closing
Across the wholesale network, a standalone HELOC requires at least 75% of the line to be drawn at closing. That is the biggest mechanical difference from the textbook picture. You cannot open a line, leave it untouched, and pull each contractor payment as it comes due.
Interest accrues on the drawn balance. With most of the line drawn at closing, you start paying interest on a large balance before the first shovel hits dirt. Pricing also floats through both the draw and repayment periods and never converts to fixed.
So how do you stage? Three structures work in practice:
1. Size the line to the early phases. Take a line that roughly matches soft costs, site work, and framing. The 75% drawn at closing then lines up with money you are about to spend.
2. Stack lines over time. A borrower can hold up to three lines, subject to combined exposure caps. A second line comes later, after the first phases are done and the file supports it. Each one is a separate review and a separate closing.
3. Mix funding sources. Use cash for design and permits. Use the line for the heavy construction phases. Use a refinance at the end.
Subsequent draws after closing carry a $1,000 minimum in most states, higher in a few. Small contractor payments need a plan, either bundled draws or cash.
Honestly, this is a genuine trade-off. A line sized to the whole budget gives you certainty but idle borrowed cash. A smaller line costs less to carry but leaves a gap. For a short build with a firm bid, the full-size line is usually cleaner. For a long or uncertain build, staged lines or cash cover the gap.
How Underwriting Treats an ADU HELOC
Underwriting a HELOC reads the borrower and the equity. It does not read the future rent. Here is the sequence, step by step.
Step 1: Combined leverage on current value. Lenders add the first mortgage and the new line, then divide by the property’s value today. The CFPB’s HELOC booklet describes the same basic approach: a percentage of appraised value minus what you owe. Picture a first mortgage at 50% of value. On an investment property, the line can add up to 20 points of value before hitting the 70% CLTV ceiling.
Step 2: The occupancy tier. Ceilings depend on how the property is used. Most files fall in these ranges, subject to lender guidelines and full file review.
| Occupancy | Max CLTV | Min credit | Max line |
|---|---|---|---|
| Investment property | 70% | 700 | $500,000 |
| Second home | Up to 90% (720+ only) | 640 | $500,000 |
| Primary residence | Up to 90% (720+ only) | 600 | $750,000 |
The 90% figure exists only at a 720-or-better credit profile, and only on lines up to $500,000. Lower credit tiers step down to 85%, 80%, or 70% on primary residences. A line above $500,000 is primary-residence only, caps at 75% CLTV, and needs a full appraisal.
Step 3: Credit and debt-to-income. The network program floor is 600, and the report is from a single bureau tied to the primary wage earner. Debt-to-income (DTI) tops out at 50%, and 45% for profiles from 600 to 679. The lender reviews your file on the interest-only payment calculated on the maximum draw, not on what you plan to use.
Step 4: Valuation. Lines at or below $500,000 ordinarily run an automated valuation with no traditional appraisal. A higher CLTV may require a secondary valuation, and you can request a full appraisal. Either way, the value reflects the property as it stands today.
That last point trips people up. A completed ADU may support a higher appraised value, depending on comps and underwriter review. But the line is not sized on that value. If your equity today is thin, the finished project does not fix the math.
Step 5: Property and title. Eligible collateral includes single-family homes, 2-4 units, PUDs, townhomes, and condos, including non-warrantable condos. Manufactured homes, co-ops, condotels, log homes, and commercial or agricultural properties are not offered. Title must sit with you personally or in a revocable living trust.
Key Terms Defined
CLTV (combined loan-to-value): Your first mortgage plus the new line, divided by the property’s current value.
Draw period: The stretch when you can borrow from the line and pay interest only. On the network’s investment lines it runs five years.
Repayment period: The stretch after the draw period, when payments include principal. Borrowing ends here.
Subsequent draw: Any withdrawal after the opening draw at closing. It carries a minimum amount.
DSCR (debt service coverage ratio): Monthly rent divided by the full monthly payment on a rental, which includes principal, interest, taxes, insurance, and any HOA dues.
Seasoning: The waiting period a lender wants before a cash-out refinance. About 6 months is the common expectation.
Where the General Rule Breaks
The rules above cover most files. These edge cases are where good plans fall apart.
The line can be frozen or reduced. HELOCs generally let the lender freeze or cut the line if the home’s value drops or your finances worsen. On a build needing future draws, that is the central risk. Half a foundation and no money is the nightmare. Keeping the early draws large reduces your exposure here.
Rental use can be restricted. A line written on an owner-occupied home may restrict leasing. Read the occupancy and rental terms before you build a unit to rent.
LLC-owned property is out. LLCs, corporations, partnerships, and irrevocable, blind, or land trusts cannot hold title on this line, per lender program requirements. A property already deeded to an LLC needs a vesting change or a DSCR cash-out refinance instead. This is the sharpest difference from a DSCR loan.
Investment lines cap lower. An investment-property line has a 70% CLTV ceiling, a 700 minimum score, and a $500,000 maximum. There is no higher investment tier.
Thin equity. A recent buyer often has too little equity for the budget. Construction-style or renovation financing, or a second-position loan, fills that gap.
Land splits. Lenders generally want the whole parcel in the collateral. Carving off land for a detached unit complicates the file.
Exposure and availability. A borrower owning more than 15 financed properties is not eligible. This HELOC is also offered in 16 states only, which is narrower than Lendmire’s 41-market DSCR footprint.
Appraisal shortfall. Comps for ADUs can be thin, so the finished value may not match your cost. Plan the exit around what the property can support, not what you spent.
Protect Yourself When No One Inspects the Work
A construction loan releases money after an inspector confirms the work. A HELOC does not. You are the inspector.
Build the safeguards yourself:
- Tie contractor payments to milestones, not to the calendar.
- Keep deposits small. A large upfront payment leaves you exposed if work stalls.
- Collect lien waivers with every payment, so unpaid subcontractors cannot claim the property later.
- Match each draw to an invoice and keep every record.
- Verify the work against the permit inspection before releasing the next payment.
Sequence the soft costs first. Design, engineering, surveys, permits, and utility connections come before any construction. Paying them from cash or the first draw avoids starting a build you cannot finish.
What Happens When the Draw Period Ends?
Repayment begins on schedule, whether or not the unit has a tenant. The CFPB’s explanation of a HELOC notes that the draw period can last a decade on some lines. On this network, it is shorter.
Two draw structures exist on primary residences and second homes:
- A 3-year interest-only draw followed by a 17-year fully amortizing repayment.
- A 5-year interest-only draw followed by a 25-year fully amortizing repayment.
Investment lines use the 5-year draw and 25-year repayment structure only. Always read a quoted figure against its own structure.
Run a sanity check on timing. Permits, construction, and lease-up take time. A 3-year draw leaves little slack for a delayed permit. When repayment starts, payments add principal and the monthly cost steps up. Plan for that jump before you sign.
The Exit: Pay It Down or Refinance
Most investors plan one of three exits. They pay the line down from rent and savings. They refinance the first mortgage and line into one new loan. Or they refinance into a DSCR loan.
Refinancing the entire first mortgage to pull ADU cash can raise the cost on the existing balance. That is why many investors keep the first lien and add a second. Lendmire’s piece on comparing a HELOC with a cash-out refinance on a rental walks through that trade-off.
DSCR loans are designed for non-owner-occupied investment properties. Because they are business-purpose investor loans, they are reviewed differently from a standard owner-occupied mortgage. That matters here.
Here is how the DSCR side typically works across the network:
- Cash-out leverage: tops out around 75% LTV on standard rentals. A 70% cash-out ceiling applies to short-term-rental collateral.
- Seasoning: about 6 months 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.
- Credit: a 620 floor exists in parts of the network, most programs want around 660, and 700+ unlocks the strongest tiers.
How the lender counts the ADU’s rent depends on program guidelines and property review, including how the unit is classified and permitted. Confirm it before you build, not after.
One warning. Clearing 1.00 is not the same as positive cash flow. DSCR compares rent to the payment only. Repairs, vacancy, management, utilities, and capital expenses sit outside the calculation. The complete DSCR loans guide covers the math in detail.
Tax treatment can depend on how the funds are used and how the property is held; investors should keep clear records and speak with a qualified tax professional before relying on any deduction.
HELOC, or Something Else?
Choose the tool by your equity, your budget certainty, and your timeline.
| Option | Best when | Watch for |
|---|---|---|
| HELOC sized to early phases | Firm bid, solid equity | Most of the line draws at closing |
| Stacked lines | Long build, rising equity | Separate reviews, combined caps |
| Cash plus a line | Soft costs are small | Cash tied up in permits |
| Construction loan | Equity is thin | Inspection-gated draws, new terms |
| Cash-out refinance | You want one loan | Resets your first mortgage |
Here is the decision flow. If your equity covers the budget at 70% CLTV or better terms, a sized HELOC works. If it falls short, look at construction financing. If the first mortgage is cheap, keep it and add a second lien. If the property sits in an LLC, change the vesting or skip the HELOC.
Lendmire’s article Should You Tap Your Home HELOC to Fund a Rental Purchase? covers the related question of using the line for a purchase.
Frequently Asked Questions
Can I use a HELOC before construction starts to pay for permits and design?
Yes, and it is often the smartest first use. Soft costs come before any building. On this network, the line is drawn mostly at closing, so size it to cover those costs plus the first construction phases. Subsequent draws carry a $1,000 minimum in most states.
Does the lender count the ADU’s future value or rent?
Neither, for the HELOC itself. The line is sized on current value and your credit, DTI, and combined leverage. A completed ADU may support a higher appraised value later, depending on comps and underwriter review. Rent matters at the DSCR refinance stage, where program guidelines decide how the unit counts.
What if I run out of line before the ADU is finished?
Build a contingency into the budget up front, around 10% in the planning split above. If the line is exhausted, options include cash, a second line within the three-line limit, or a refinance. Combined CLTV caps still apply, so a second line is not guaranteed.
Can I rent the ADU if I borrowed against my primary residence?
Possibly, but read the occupancy and rental terms first. Lines on owner-occupied homes can restrict leasing. For a pure rental property, an investment-occupancy line carries a 70% CLTV ceiling, a 700 minimum score, and a $500,000 maximum.
Is a HELOC the right choice if my property is held in an LLC?
Not directly. LLCs, corporations, partnerships, and irrevocable, blind, or land trusts cannot hold title on this line. A vesting change into your name or a revocable living trust may open the door, or a DSCR cash-out may fit better. Eligibility depends on lender guidelines.
Next Step: Run Your Numbers
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 illustrative calculator on the site can give you a rough estimate to start from. Lendmire is a broker and arranges these loans through select lenders in its wholesale network, and all terms are subject to lender guidelines and full file review.
About Lendmire
As a mortgage broker (NMLS# 2371349), Lendmire helps homeowners and real estate investors in its 16 full-service states open home equity lines of credit arranged through wholesale lenders. Lendmire is never the lender; line amounts, ceilings and terms are set by the lender under its guidelines. Scotsman Guide named Lendmire a Top Mortgage Workplace in both 2025 and 2026.
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References
1. Urban Institute – To Increase the Housing Supply, Focus on ADU Financing
3. CFPB – What is a home equity line of credit (HELOC)?
This article is part of Lendmire’s home equity line of credit program — full qualification details, guidelines, and scenarios live on the program page.
Related reading: How to Fund an ADU With a HELOC Behind a Low First Mortgage · How to Draw a Rental HELOC in Stages During a Rehab · How to Finance an ADU With a First-Lien HELOC on a Paid-Off Home
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.