How to Finance an ADU: Loans, HELOCs, and More

What Makes ADU Financing Different

Financing an ADU is more complex than financing a home purchase. You're borrowing against an existing property to build something that doesn't exist yet — which means lenders need to value the project differently.

The good news: ADU-specific financing has improved dramatically since 2022. Several lenders now offer products designed specifically for ADU construction, and some states offer subsidized programs for income-qualifying homeowners.

Option 1: HELOC (Home Equity Line of Credit)

A HELOC lets you borrow against your home equity as needed — like a credit card secured by your house.

How it works: Your lender sets a credit limit based on your home value minus your mortgage balance. You draw funds as you need them during construction and pay interest only on what you've drawn.

Best for: Homeowners with significant equity who want flexibility. HELOCs are ideal because ADU construction costs come in stages — you don't need all the money upfront.

Typical terms:

• Draw period: 5–10 years (interest only)
• Repayment period: 10–20 years
• Rate: Variable, typically prime + 0.5–2%
• Closing costs: Low ($500–$2,000)

Drawbacks: Variable rate means your payment can rise if rates increase. Requires substantial existing equity — most lenders cap total borrowing at 80–85% of home value.

Option 2: Cash-Out Refinance

Replace your existing mortgage with a larger one and pocket the difference in cash.

How it works: If your home is worth $800,000 and you owe $400,000, you might refinance into a $600,000 mortgage and use $200,000 to build your ADU.

Best for: Homeowners who want a fixed rate and have a higher-rate existing mortgage worth refinancing anyway.

Typical terms:

• Fixed rate (30-year typical)
• Closing costs: 2–5% of loan amount ($8,000–$20,000 on a $400K loan)
• Requires full underwriting

Drawbacks: Resets your mortgage clock. If you're 10 years into a 30-year mortgage, you go back to 30. Closing costs are high. Only makes sense if you can improve your rate or have no other good options.

Option 3: ADU Construction Loan

Specialized products designed specifically for ADU projects. Relatively new — available primarily in California, Colorado, and a few other states.

How it works: Lenders like RenoFi underwrite your loan based on the after-renovation value of your property (what it'll be worth once the ADU is built) rather than current equity. This lets you borrow significantly more.

Best for: Homeowners who don't have enough current equity for a HELOC or cash-out refi but have a strong project with high expected value.

Typical terms:

• Rates: Slightly higher than traditional mortgages (7–10%)
• Loan limits: Up to $500,000 in high-cost markets
• Construction draws: Funds released in stages as construction milestones are met

Drawbacks: More complex underwriting. Requires detailed project plans and contractor bids upfront.

Option 4: State and Local Programs

Several states offer subsidized ADU financing for income-qualifying homeowners:

California: CalHFA ADU Grant Program offers up to $40,000 for pre-development costs (design, permits, site prep) for income-qualifying homeowners.

Colorado: The Colorado ADU Finance Program offers below-market rate loans through participating lenders.

Oregon: Portland has historically offered SDC waivers and some financing assistance through Portland Housing Bureau programs.

Check your state housing finance agency (HFA) website for current programs — these change frequently.

Option 5: Personal Loan

Unsecured loan based on creditworthiness rather than home equity.

Best for: Smaller projects (garage conversions, JADUs) where the loan amount is under $100,000.

Typical terms:

• Rate: 8–20% depending on credit
• Term: 3–7 years
• No closing costs, fast funding

Drawbacks: Much higher interest rates than home equity products. Payments are significant on larger amounts.

Comparing Your Options

Option	Best For	Rate Type	Typical Rate	Closing Costs
HELOC	Staged draws, flexibility	Variable	Prime + 1%	Low
Cash-out refi	Fixed rate, refi opportunity	Fixed	6–8%	High
ADU construction loan	Low equity, high project value	Fixed	7–10%	Medium
State program	Income-qualifying homeowners	Fixed (subsidized)	3–5%	Low
Personal loan	Small projects	Fixed	8–20%	None

How Much Can You Borrow?

Most lenders cap total borrowing at 80–85% of your home's current or after-renovation value. Here's a quick example:

• Home value: $700,000
• Current mortgage: $350,000
• Max total borrowing (80%): $560,000
• Available for ADU: $560,000 - $350,000 = $210,000

If your ADU costs $250,000, you'd need to either put in $40,000 cash, find an ARV-based lender, or look at state programs.

Use our cost calculator to estimate what your ADU will cost, then run the ROI numbers to make sure the math works.

Tips Before You Apply

1. Pull your credit — know your score before applying. Above 720 gets the best rates.
2. Get a full appraisal — not a Zestimate. A licensed appraiser's ARV estimate makes a real difference with construction lenders.
3. Have plans ready — lenders want to see permitted drawings or at least architect plans before committing.
4. Get multiple quotes — ADU financing rates vary significantly by lender. Compare at least 3.
5. Understand the draw schedule — make sure your lender's draw process matches your contractor's payment schedule.