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Nick Nagy · ADU financing

Nick Nagy finances an ADU without touching your first mortgage.

A homeowner sitting on a low first-mortgage rate does not have to refinance it to build an ADU. A HELOC, a HELOAN or a later DSCR refinance can each fund a different stage of the project.

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The answer

The direct answer

Building an accessory dwelling unit does not require refinancing the first mortgage, which matters most to a homeowner whose existing terms are years old and better than today’s market. A home equity line of credit can fund a construction project in draws as milestones are met, a home equity loan can fund a prefabricated unit purchased in one lump sum, and a DSCR refinance can later replace either of those once the finished ADU has a paying tenant.

What I tell people first

I match the financing tool to the stage of the project, not the other way around. A stick-built ADU with a permitting and construction timeline usually fits a HELOC’s draw schedule better than a lump sum. A prefabricated unit that arrives and installs quickly usually fits a HELOAN. Once the unit is done and rented, I look at whether a DSCR refinance sized to its own rent makes sense to pay off the construction debt. Getting this sequencing right up front avoids paying for a lump-sum loan on a project that would have fit a draw schedule better, or the other way around.

Who this page is for

This page is for you if you own your home outright or with meaningful equity, and you want to add an ADU for rental income, a family member, or resale value, without giving up the rate on your existing first mortgage. It fits a homeowner comfortable managing a construction draw schedule as well as one who would rather buy a prefabricated unit and skip most of that process. It also fits a homeowner who already has a permitted ADU plan in hand and just needs the right financing structure to match the build timeline.

The fact this page stands on
California’s Department of Housing and Community Development is the state’s designated authority on local ADU ordinances, and its statewide ADU Handbook was last updated in March 2026.
Source
California HCD, Accessory Dwelling Units, hcd.ca.gov, read September 6, 2026.
Last verified
September 6, 2026
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Nick Nagy, mortgage broker and loan officer at Loan Factory
Nick Nagy NMLS #314880 · CA DRE #01444600 · Loan Factory, Inc. · 23 years About Nick · Licences, verified at source · Text 916-805-1933

Part of the Nick Nagy pages on go.homeaccesslist.com, and of the California Mortgage Answer Desk.

How it works

Why the first mortgage usually stays put

A homeowner with a materially lower rate on their existing first mortgage than current market rates has a strong reason to avoid a cash-out refinance that would replace that entire loan. A second-position loan, a HELOC or a HELOAN, leaves the first mortgage exactly as it is and only adds financing sized to the ADU project itself.

The detail that matters

HELOC versus HELOAN for construction

A HELOC is a revolving line that draws in stages as construction milestones are completed, which fits a stick-built ADU where the budget gets spent over months rather than all at once. A HELOAN is a fixed-rate loan funded in a single lump sum, which fits a prefabricated unit purchased and installed in one transaction.

How it works

Refinancing into the finished ADU’s own rent

Once an ADU is built and rented, its own income can support a DSCR refinance sized to replace the construction debt, without requiring the homeowner’s personal income to qualify for that piece. This is the same DSCR structure used on a standalone rental property, applied here to a unit on the same lot as the primary home.

The detail that matters

California’s role in the ADU landscape

California’s Department of Housing and Community Development is the state’s designated authority on local ADU ordinances, and it maintains a statewide ADU Handbook that was last updated in March 2026. Local permitting timelines and requirements still vary by city, which is part of why I ask about the permitting stage before recommending a financing structure. I check the specific city’s own permitting requirements as part of every file, since the state sets a floor, not a single statewide process.

How it works

Where this pairs with an SB 9 or AB 1033 project

A homeowner splitting a lot under SB 9 or subdividing an ADU into its own condominium under AB 1033 is often financing a related but distinct project at the same time. I look at all three together when a property is touching more than one of these programs at once, rather than treating each as a separate conversation. A property touching two of these programs at once usually needs its financing sequenced around whichever legal process moves first.

The detail that matters

The permitting clock, and why it matters for financing

California law requires a local agency to approve or deny a complete accessory dwelling unit permit application within 60 days when the lot already has an existing single-family or multifamily home on it, or the application is deemed approved by default (Government Code section 65852.2(a)(3)(A), leginfo.legislature.ca.gov, read September 6, 2026).

That statutory clock helps set realistic expectations for a HELOC draw schedule, since construction usually cannot start meaningfully earlier than the permit clears. A HELOAN funding a prefabricated unit purchased outright is less exposed to permitting timing in the same way.

Local building department workloads still vary widely by city, so I treat the 60-day statutory ceiling as the outer limit, not the typical experience.

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Files like these

Three files, and what changed the answer

An owner building a detached ADU in the backyard

The build is financed with a HELOC drawn in stages as construction milestones are met, leaving the first mortgage untouched.

An owner purchasing a prefabricated unit

The unit is paid for in one lump sum through a fixed-rate second loan, rather than a construction draw schedule.

An owner refinancing after the ADU is finished and rented

Once the ADU has a paying tenant, the construction debt is replaced with a DSCR refinance sized to the new unit’s own rent.

None of these is a promise about your file. They are shapes. The number on your own file comes from running it, which is the point of the form on this page.

Where it goes wrong

The mistakes, and none of them is the buyer

More about Nick

The rest of the Nick Nagy pages

Every question on the desk sits at the California Mortgage Answer Desk. Run your own numbers at nickfunds.com.
Nick Nagy, mortgage loan originator, Loan Factory, Inc.
Who answers

Nick Nagy

23 years in California lending · NMLS 314880 · CA DRE 01444600 · Loan Factory, Inc.

Dual licensed, so the loan side and the real estate side of a move get looked at as one problem instead of two. Most of what goes wrong in a move is a timing problem wearing a financing costume, and it is cheaper to catch it before you write an offer than after.

Financing is placed through Loan Factory, Inc. Real estate work is under CA DRE 01444600. More about Nick.
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The desk behind the file

One file, 237 lenders competing for it, and a broker who has done this for 23 years.

Loan Factory, Inc. is the brokerage. These are its published figures.

20,907+Loan Factory Google reviews
5.0Loan Factory average rating
237Lenders available through Loan Factory
48States Loan Factory is licensed in

A retail bank has one guideline book. A broker shops the same file across the shelf and finds the lender whose box it already fits.

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Straight answers

Questions people here actually ask

The follow-on questions, answered in the order they get asked.

ADU financing California

ADU financing in California typically uses a second-position loan, a HELOC or a HELOAN, so the homeowner’s first mortgage stays untouched, with a DSCR refinance available later once the finished ADU is renting.

What is an ADU HELOC?

It is a home equity line of credit used to fund ADU construction in draws as milestones are completed, rather than a single lump sum, which fits a phased build timeline.

What is the best ADU construction loan in California?

It depends on the build type. A phased stick-built project usually fits a HELOC’s draw schedule, while a prefabricated unit purchased in one transaction usually fits a HELOAN lump sum.

Can I refinance an ADU once it is built?

Yes. A DSCR refinance sized to the ADU’s own rent can replace the construction debt once the unit is complete and has a paying tenant.

Do I have to refinance my first mortgage to build an ADU?

No. A HELOC or HELOAN sits in second position behind your existing first mortgage, which stays exactly as it is.

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Mortgage loan originator, NMLS 314880, and licensed real estate salesperson, CA DRE 01444600, both under Loan Factory, Inc. 20,907+ Google reviews · 5.0 average · 237 lenders, the company's own published figures.

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  3. You get the number and keep it. A straight answer on what your file supports and what it does not. If waiting is the better move, that is the answer you get, and the numbers are yours either way.
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California HCD, Accessory Dwelling Units www.hcd.ca.gov/building-standards/adu