Most California homeowners finance an ADU with the equity in their home: a home equity line of credit, a cash-out refinance, or a construction or renovation loan. Which one fits depends on how much equity you have, your current mortgage rate, and whether you want to borrow against the finished value of the ADU. Here are the options side by side, plus where the state’s ADU grant program stands.
ADU financing options compared
| Option | How it works | Best when | Watch out for |
|---|---|---|---|
| Cash | Pay as you go | You have savings and want no debt | Keep a contingency for site surprises |
| Home equity line of credit (HELOC) | Borrow against existing equity; draw as needed | You have strong equity and want to keep your first mortgage | Usually a variable rate; borrowing limited to today’s value |
| Cash-out refinance | Replace your mortgage with a larger one | Current rates are near or below your existing rate | Gives up a low existing rate; closing costs |
| Renovation loan | Mortgage based on the home’s value after the ADU is built | You have limited equity today | More paperwork; lender must approve your builder and plans |
| Construction loan | Short-term loan paid out in draws as work is completed, then converted or refinanced | Larger projects and site-built ADUs | Draw schedules don’t always fit a factory deposit; ask early |
| Builder or factory financing | Offered by some prefab ADU companies or their lending partners | Convenience and one point of contact | Compare the rate and terms with a bank |
A prefab-specific issue: factory deposits
Factories usually require deposits and progress payments before the unit ships, while many construction loans only pay for work completed on your lot. Before you sign with a builder, ask your lender how they handle off-site construction payments. This one question heads off a common prefab financing delay.
The CalHFA ADU Grant Program
The California Housing Finance Agency’s ADU Grant Program has provided up to $40,000 to eligible homeowners for pre-development costs: architectural design, permits, impact fees, soil tests, surveys, energy reports and utility hookups. CalHFA reported its funding as fully allocated in December 2023, with 2,581 active project reservations as of November 20, 2024 (CalHFA ADU outcome report). No new round had been announced as of mid-2026. Check CalHFA for any new funding, but don’t plan your budget around it.
Let the ADU help pay for itself
- Rental income: junior ADUs and most new ADUs must be rented for terms longer than 30 days, which suits steady long-term tenants.
- Lower fees for smaller units: staying under 750 sq ft avoids impact fees; 500 sq ft or less avoids school fees.
- Property tax: only the ADU’s value is added to your assessment; your home keeps its existing base value.
Frequently asked questions
Can I finance an ADU with no equity?
A renovation loan based on the home’s value after the ADU is built is the usual route. Ask lenders whether they will count future ADU rental income.
Is there a California grant for ADUs?
CalHFA’s ADU Grant Program has offered up to $40,000 for pre-development costs, but CalHFA reported its funding fully allocated in December 2023. Check CalHFA for any new round.
Do prefab ADU companies offer financing?
Some do, directly or through lending partners. Compare their offer against a bank or credit union, and confirm how factory deposits are handled.
Want help pricing your project before you talk to a lender? Call (800) 806-7485. Related: What a prefab ADU costs in California.
By Matt Banes, iModular.com. California modular building specialist with 38 years in the industry. Last updated: October 7, 2026. General information, not financial advice; talk to a licensed lender about your situation.
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