How to Finance an ADU in California: Cash-Out, HELOAN, or Construction Loan
Building a casita in the backyard sounds simple until you get to the part nobody enjoys: writing the check. A permitted ADU in Los Angeles County usually lands somewhere between $150,000 and $400,000, and the number swings hard depending on size, whether you're converting a garage or building from dirt, and how steep your lot is. Most homeowners don't have that sitting in savings, so the real question isn't whether to borrow — it's which of three loans fits your situation. Each one prices differently, and the right pick usually comes down to the rate on the mortgage you already have.
See how cash-out refinancing worksQuick answer
Most homeowners finance an ADU one of three ways. A cash-out refinance replaces your current mortgage with a bigger one and hands you the difference in cash — best when your existing rate is already near today's market. A fixed-rate home equity loan (HELOAN) sits behind your first mortgage and leaves it untouched, which is the usual pick when you're holding a low pandemic-era rate you don't want to lose. A construction or renovation loan qualifies partly off the home's future value after the ADU is built, so it can fund bigger projects — with more paperwork, inspections, and draws along the way.
What you'll learn
- What a permitted ADU actually costs in LA County, and why the range is so wide
- Cash-out refinance vs. HELOAN vs. construction loan — when each one wins
- Why the rate on your current mortgage decides more than anything else
- Whether future rent from the ADU helps you qualify (mostly it doesn't, up front)
- The permit and timeline reality in Los Angeles before you count on the money
What an ADU actually costs in LA County
Prices vary a lot, so treat any single number with suspicion. A garage conversion — keeping the existing walls and roof — is the cheap end, often in the low six figures. A ground-up, detached one- or two-bedroom unit with its own foundation, plumbing run, and utility connections is the expensive end. On top of the build itself you're paying for design, permits, city fees, and sometimes a sewer or panel upgrade the city requires before it signs off. A realistic planning range for a permitted ADU here is roughly $150,000 to $400,000, and the honest answer is that yours won't be known until you have real bids in hand.
- Garage or interior conversion — lowest cost, since the shell already exists
- Prefab or modular unit — mid-range, faster to install once the site is prepped
- Detached ground-up build — highest cost, especially on a sloped or tight lot
- Site work extras — sewer, electrical panel, and grading that the city may require
Every figure here is illustrative for planning only. Get contractor bids before you size a loan around a number.
Option 1: Cash-out refinance
A cash-out refinance replaces your existing mortgage with a new, larger one and pays you the difference at closing. If your home is worth $900,000 and you owe $400,000, a lender might let you refinance up to about 80% — $720,000 — leaving roughly $300,000 in cash after your old loan is paid off. The catch is that you're resetting the rate on your entire balance, not just the new money. That's fine if your current rate is already near where cash-out refinance rates sit today. It hurts if you're sitting on a 3% loan, because you'd be trading that whole balance up to today's rate just to reach the equity. For people asking how fast they can refinance, a clean cash-out typically closes in about 30–45 days.
Best when: your current mortgage rate is already close to today's rates, so raising your balance doesn't cost you a cheap rate you'd rather keep.
Option 2: Fixed-rate home equity loan (HELOAN)
A HELOAN is a second loan that sits behind your first mortgage. Your original loan — rate, balance, term — stays exactly as it is, and you take a separate fixed-rate loan against your equity with its own predictable monthly payment. This is the move for the millions of owners holding a 2–3% pandemic-era rate who won't refinance into today's market to fund a project. That refusal has a name people in the business use — the lock-in effect — and it pushed second-lien lending to an 18-year high, per ICE's June 2026 mortgage monitor. A HELOAN's rate is higher than a first mortgage's, but it only applies to the ADU money, not your whole balance, which is often the cheaper deal overall.
Best when: you're keeping a low first-mortgage rate and want a fixed payment on just the ADU money. A HELOC (a line of credit) is a variable-rate cousin some owners use for the same reason.
Option 3: Construction or renovation loan
Construction and renovation loans are built for exactly this — adding square footage or a whole unit. Their edge is that they can qualify partly off the home's future value, once the ADU is finished and appraised, instead of only today's equity. That matters when you don't have enough equity yet to cover the build. The trade-off is more moving parts: the lender approves a budget, releases money in stages (called draws) as work gets done, and sends an inspector to verify each phase. There's more paperwork, and the timeline stretches to match the build. For a large ground-up ADU with limited existing equity, though, it's often the only path that reaches the full number.
Best when: the project is big, your current equity won't cover it, and you're willing to trade simplicity for the ability to borrow against the finished value.
Comparing the three side by side
Here's the quick version. Read the table as a starting map, not a quote — your actual terms depend on your equity, credit, income, and the property.
| Feature | Cash-out refinance | Home equity loan (HELOAN) | Construction / renovation loan |
|---|---|---|---|
| Touches your first mortgage? | Yes — replaces it entirely | No — leaves it untouched | Depends on program; often a new first loan |
| Best when your current rate is… | Near today's rates | Low — worth protecting | Either — driven by project size |
| Qualifies off… | Today's equity | Today's equity | Future value after the ADU is built |
| Payout | Lump sum at closing | Lump sum at closing | Staged draws during the build |
| Rate type | Usually fixed | Fixed | Varies by program |
| Extra steps | Standard refi | Light — second lien | Inspections and draw schedule |
Illustrative comparison only — not a rate quote or approval. Terms depend on your equity, credit, income, and property.
Can the ADU's future rent help me qualify?
This is the hope almost everyone raises, so here's the straight answer: mostly no, not up front. Lenders qualify you on income you can document today — pay stubs, tax returns, existing rents — and a unit that doesn't exist yet has no rent history to count. Some programs will use a portion of projected market rent once the ADU is permitted and appraised, but you generally can't lean on it to get the loan approved before you build. Plan the financing around income you already have, and treat the future rent as the upside that makes the payment easier later — not as part of the qualification math today.
Permits and timeline: the LA reality
California has pushed cities to approve ADUs faster, and Los Angeles has to act on a complete application within 60 days. That's the plan-check clock — not the whole project. Between drawing plans, getting them approved, and actually building, most ADUs here take roughly a year from first sketch to final sign-off, longer for a ground-up unit or a tricky lot. That timeline matters for financing: a construction loan is built to stretch across it with staged draws, while a cash-out or HELOAN hands you the money up front and expects payments to start right away, whether or not the ADU is done. Line up the loan type with how the build will actually unfold.
California HCD — ADU information and state lawHow Miguel helps you pick
The right loan isn't a matter of opinion — it's a matter of your numbers. Miguel A. Vazquez (NMLS #401212) is a bilingual mortgage broker who runs all three options against your real situation: your current rate and balance, your equity, your documentable income, and what the ADU will cost. Sometimes the answer is obvious — a 2.75% first mortgage almost always argues for a HELOAN over a cash-out. Other times it's a genuine toss-up worth modeling both ways. Because a broker shops multiple lenders instead of one bank's menu, you see the real trade-offs side by side in English or Spanish, then choose with the whole picture in front of you.
Key takeaways
- ADU costs in LA County typically run $150,000–$400,000, but a garage conversion and a ground-up two-bedroom can sit at opposite ends of that range.
- A cash-out refinance makes sense when your current mortgage rate is already close to today's rates, since you're rewriting the whole loan anyway.
- A fixed home equity loan (HELOAN) keeps your low first-mortgage rate intact — the reason second-lien lending hit an 18-year high in 2026 as owners refused to give up 3% rates.
- Construction and renovation loans can qualify off the home's value after the ADU is finished, which funds larger builds but adds inspections, draws, and time.
- Lenders generally won't count the ADU's future rent to help you qualify up front, so plan the loan around income you can already document.
Common questions
How much does it cost to build an ADU in Los Angeles County?
Plan on roughly $150,000 to $400,000 for a permitted ADU, though the range is wide. A garage conversion sits at the low end because the shell already exists; a detached, ground-up one- or two-bedroom unit with its own foundation and utilities sits at the high end. Design, permits, city fees, and any required sewer or electrical upgrades add on top. Get contractor bids before you size a loan — every figure here is illustrative for planning only.
Should I use a cash-out refinance or a home equity loan for my ADU?
It usually comes down to your current mortgage rate. If your rate is already near today's rates, a cash-out refinance is clean — you rewrite the whole loan and take the difference in cash. If you're holding a low pandemic-era rate, a fixed home equity loan (HELOAN) is typically the smarter pick because it leaves that cheap first mortgage untouched and only charges the higher rate on the ADU money. That lock-in effect is exactly why second-lien lending hit an 18-year high in 2026.
Can I qualify for the loan using the rent I'll collect from the ADU?
Usually not at the start, but the timing matters. The trigger is a completed permit and a fresh appraisal that captures the ADU's projected market rent — once those exist, some programs will credit a portion of that projected income toward qualifying. Before that point, there's no rent history to count and lenders work entirely from documented income you have today. That trigger is also why a construction loan that converts to a permanent mortgage at the end of the build can sometimes let you use rental income sooner than a lump-sum loan. Plan your initial qualification on existing income, then ask specifically about rental income at the conversion step.
How long does an ADU take to build in Los Angeles?
Los Angeles must act on a complete ADU application within 60 days, but that's just the plan-check step. Counting design, approval, and construction, most ADUs here take roughly a year from first sketch to final sign-off — longer for a ground-up unit or a difficult lot. That timeline is why a construction loan, which releases money in stages as the build progresses, fits big projects better than a lump-sum loan that starts charging payments right away.
Which loan lets me borrow against the ADU's future value?
A construction or renovation loan. Unlike a cash-out refinance or a HELOAN — both of which lend against your equity today — a construction loan can qualify partly off the home's appraised value after the ADU is finished. That's what makes it work when your current equity won't cover the build. The trade-off is more paperwork, staged draws, and inspections along the way, plus a timeline that matches the project.