California homeowners actually have a solid number of ways to fund an ADU.
Depending on how much equity you have, your credit situation, and how big the project is, you could use a home equity line, a loan that prices in the ADU’s future value, a Fannie Mae renovation product, or, in a good timing window, a state grant.
Here’s a breakdown of the six main paths worth knowing about.
At a Glance: All Six Options
| Option | Type | Replaces Current Mortgage? | Best For |
| HELOC | Revolving credit line | No | Flexible, phased spending |
| Cash-out refinance | Lump sum via new loan | Yes | Large equity, big projects |
| Construction loan | Staged disbursements | Converts (or requires 2nd closing) | New builds, lower equity |
| Home equity loan | Fixed lump sum | No | Clearly defined budgets |
| Fannie Mae HomeStyle | Combined purchase + reno | Yes (purchase) | Buy and build together |
| CalHFA Grant | No-repayment grant | No | Pre-development costs |
1. Home Equity Line of Credit (HELOC)
A HELOC draws on the equity built into your home, functioning more like a revolving credit line than a traditional loan.
You pull funds as you need them during the draw period, which typically runs 10 years (some lenders offer shorter windows starting around five), and you pay interest only on what you’ve used.
That means you can cover architectural design costs up front, then draw again for permits, then again as construction starts.
Variable interest rates are the trade-off here. Monthly payments can fluctuate as the market moves, making budgeting less predictable.
That said, this option leaves your existing mortgage untouched and tends to be a good fit for homeowners with substantial equity who want flexibility throughout a project.
2. Cash-Out Refinance
A cash-out refinance replaces your current mortgage with a new, larger loan, and you receive the difference as a lump sum to put toward construction.
If your home is worth $650,000 and you owe $300,000, you might refinance for $500,000 and walk away with $200,000 in cash.
A few things worth thinking through before going this route:
- Your current interest rate vs. the new one. In a higher-rate environment, this trade can be costly.
- Your remaining equity. Most lenders cap conventional cash-out refinances at 80% of your home’s value.
- Projected ADU rental income. Does it offset the higher monthly payment?
For homeowners who bought their property years ago and are sitting on significant appreciation, the cash-out refinance can unlock meaningful funding power. Just run the numbers carefully before signing.
3. ADU Construction Loans
There are two versions of construction financing worth distinguishing.
A construction-to-permanent loan funds the build in staged disbursements as each phase of construction is completed, then automatically converts to a traditional mortgage when the ADU is finished.
A stand-alone construction loan works similarly during construction but requires a separate mortgage application and a second closing once the project is complete, which means two sets of closing costs.
What sets ADU-specific construction products apart from standard options is that many lenders now allow borrowing against the property’s projected future value. That opens things up for homeowners who don’t yet have a large equity cushion.
If you’re still sorting out the permit process before approaching lenders, there’s a solid walkthrough on getting your ADU permitted in California worth reading first.
4. Home Equity Loan
A home equity loan also draws on your existing equity but delivers a single fixed lump sum at a fixed interest rate.
It runs alongside your current mortgage without replacing it, and your monthly payment stays the same throughout the loan term.
This works well when your ADU budget is locked in, and you don’t need the flexibility of drawing funds over time. The predictability is the advantage.
The downside: you need meaningful equity to qualify, and most lenders cap combined loan-to-value at around 85% of your home’s value.
5. Fannie Mae HomeStyle Renovation Loan
The Fannie Mae HomeStyle Renovation Loan bundles purchase and construction costs into a single mortgage, making it especially useful if you’re buying a property and planning to add or convert an ADU right away.
Garage conversions qualify. Fannie Mae’s Selling Guide explicitly lists accessory units and garages as eligible structures. This matters in Southern California, where converting an existing garage is often the most cost-effective starting point.
Qualification requirements follow standard Fannie Mae guidelines: solid credit, verified income, and a lender approved to originate the product.
The appeal is the simplicity of handling everything in one transaction rather than juggling multiple loan products at once.
6. CalHFA ADU Grant Program
The California Housing Finance Agency’s ADU Grant offered qualifying homeowners up to $40,000 to reimburse pre-development costs. That includes architectural plans, permit fees, property surveys, soil tests, utility hookups, and energy reports.
To be eligible, homeowners needed to meet CalHFA’s income limits.
The most recent round of funding was fully allocated on December 28, 2023, and as of this writing, the program is not accepting new applications. CalHFA has also posted warnings that anyone claiming to help you access grant funds right now is running a scam.
No relaunch date has been confirmed, but the program has opened multiple rounds since its 2021 launch and is worth monitoring if you’re still in the early planning stages.
Frequently Asked Questions
Can projected ADU rental income help me qualify for a loan?
Some lenders, particularly those offering ADU construction loans, will factor in projected future rental income when calculating your loan amount. It’s worth asking about this upfront, because it can meaningfully raise your borrowing ceiling.
How much equity do I need to get started?
Most equity-based products require you to retain at least 15% to 20% in the home after the loan closes. Construction loans that base the amount on future value tend to be more accessible for homeowners who haven’t yet built a large equity cushion.
Are garage conversions eligible for all these financing options?
Yes. Garage conversions qualify for most of the products above, including construction loans and the HomeStyle program. Because they typically cost less than a new detached build, the loan amounts tend to be lower too, which can make qualification more straightforward.
The Part Where You Realize There’s a Shortcut
Between comparing loan structures, chasing down grant windows, and budgeting in soft costs before a single permit is filed, the financing research alone can take weeks.
If you’d rather put that energy into actually planning your ADU, take a look at what Cornejo’s Builders in Southern California, or call us at (562) 319-3178 or message us here.