Skip to content
OwnAdu

Phase 04 of 06

Phase 4: Financing your ADU

Almost no one pays cash for an ADU. Picking the right loan product — and timing the application correctly — can save tens of thousands of dollars and weeks of schedule risk. Six paths get used in practice; here's how to choose.

Typical duration

3–8 weeks (run in parallel with design or permitting)

Typical phase cost

$2,000–$8,000 in origination + closing costs

The six financing paths that actually get used

Most ADU homeowners use one of six products, often in combination. Run your specific numbers in our loan calculator.

1. HELOC (Home Equity Line of Credit)

Variable-rate revolving credit secured by your home equity. Best for homeowners with substantial equity who want to draw cash as construction progresses. Per Dynamic Quality Builders' 2026 financing breakdown, current HELOC rates run roughly prime + 0.5% to 2% (variable), with loan amounts up to 85% of home equity and 10-year draw periods typical.

  • Pros: low/no closing costs, fast approval, interest-only payments during draw.
  • Cons: variable rate, exposed to rate increases, usually capped at 80–90% combined LTV.
  • Best when: you have 30%+ equity and your existing first mortgage is at a low rate you don't want to disturb.

2. Home equity loan

Lump-sum fixed-rate second mortgage. Predictable payments, but you commit to the full amount up front. Fixed rates in 2025–2026 trended around 7–10% (Golden State ADUs 2025).

  • Best when: you have a firm builder quote and want fixed payments.

3. Cash-out refinance

Replace your existing mortgage with a larger one and take the difference. Best when your current mortgage rate is high relative to today's rates. Most lenders allow up to 80% LTV on cash-out refis.

  • Pros: single fixed payment, long term, often the lowest blended rate.
  • Cons: closing costs on the entire balance; you reset your mortgage clock.
  • Best when: your current mortgage rate is above today's market and you have substantial equity.

4. Construction loan

Draw-based financing during construction that usually converts to a permanent mortgage at completion. Per Better Place Design Build's 2025 breakdown, construction loans typically price at prime + 1–3% during the build, then convert.

  • Pros: matches how you actually pay builders (in stages).
  • Cons: higher rate during construction, more paperwork, requires permits in hand before funding.
  • Best when: you don't have a HELOC cushion and need staged funding aligned with builder draws.

5. Renovation loan (FHA 203k or Fannie Mae HomeStyle)

A single mortgage that covers your existing home and the ADU construction. Fannie Mae HomeStyle and the FHA 203(k) program both explicitly allow ADU construction. Per Golden State ADUs (2025), both products allow lower equity than HELOC and roll renovation costs into the mortgage at standard mortgage rates.

  • Pros: lower rates than HELOC, lower equity requirement, single mortgage.
  • Cons: stricter contractor requirements, longer underwriting, more paperwork.
  • Best when: you're buying or refinancing simultaneously, or you don't have enough equity for HELOC.

6. Reverse mortgage (HECM)

If you're 62 or older and own your home outright or have significant equity, a reverse mortgage provides tax-free funds without monthly repayments. Useful in multi-generational ADU setups (Golden State ADUs, 2025).

  • Best when: retirees building a rental unit for income or family with no plan to sell.

The Fannie Mae and Freddie Mac game-changer

As of 2024, Fannie Mae and Freddie Mac formally allow lenders to factor projected ADU rental income into loan qualification — meaning you can qualify for a larger loan if the ADU is going to generate documentable rental income. This is the single biggest lending shift in recent years, and it's why ADU-aware lenders can underwrite higher loan-to-value ratios than they could just a few years ago.

The practical question to ask any lender: "Do you underwrite ADU rental income on the appraised value, and do you accept the appraiser's 1007 fair market rent schedule?" If the answer is yes, you're working with an ADU-friendly institution. If no, find a different lender.

Grants and state-level programs

California's CalHFA ADU Grant Program historically offered up to $40,000 in reimbursement for pre-development costs (architectural designs, site prep, permits, soil tests, impact fees, property surveys, energy reports) for qualifying low- and moderate-income homeowners.

Status as of May 2026: Per the official CalHFA ADU page, the latest round of funding was fully allocated on December 28, 2023, and the agency has not announced a new funded round since. Treat the grant as paused/exhausted unless and until CalHFA announces fresh funding. CalHFA explicitly warns of scammers claiming they can secure the grant for homeowners — they cannot; the program is administered through CalHFA-approved lenders only when funded. Last verified by OwnAdu against calhfa.ca.gov/adu: May 14, 2026.

Other state-level options to investigate:

  • Washington state's $25,000 ADU grant in some counties.
  • San Diego Housing Commission's 1% loan option (cited by Better Place Design Build 2025) for qualifying homeowners.
  • SB 1164 (California, 2025): 15-year property tax exemption on new ADUs — not a grant but materially reduces the carrying cost.
  • City-level fee waivers, especially for units under 750 sq ft.

Don't build your budget assuming you'll get one of these. Check eligibility — they're real money when they apply, but unreliable as a primary funding strategy.

The right time to apply

HELOCs and cash-out refinances can be applied for any time after you have a working budget. Construction loans and renovation loans need approved permits or near-permits to fund. The optimal sequencing for most homeowners:

  1. During Phase 1 (planning), get informally pre-qualified for one or two products.
  2. During Phase 2 (design), submit the formal HELOC or refi application if going that route — these don't need permits.
  3. During Phase 3 (permits), submit the construction or renovation loan application — funding should line up with permit approval.

What lenders need from you

  • Recent W-2s and tax returns (2 years for most products)
  • Asset statements (bank, brokerage, retirement) for 2 months
  • Existing mortgage statement and payoff information
  • Permits or detailed scope of work for construction-tied loans
  • Builder bid and qualifications for renovation loans
  • Appraisal (typically ordered by the lender)
  • For projected rental income: a fair market rent schedule (1007 form) from the appraiser

One model worth knowing: builder payment coverage

Some California design-build firms now cover the homeowner's monthly loan payment during construction and add it to the project cost at completion. Dynamic Quality Builders publishes their version explicitly: the firm covers $1,000–$1,800/month for the 3–6 month build, the covered payments are added to the final invoice, and the homeowner pays nothing out of pocket until they receive keys. This is a real product, but the financing math means you're effectively borrowing those payments from your builder at construction-loan rates. Compare carefully against a pure HELOC strategy.

Once funding is locked and permits are in hand, you're ready for Phase 5 — Construction.

Have questions about your phase 04 decisions?

Get the free Homeowner's Playbook — full breakdown of every phase, with checklists.

By submitting, you consent to OwnAdu and up to three vetted ADU builders contacting you by email about your project. Consent is not a condition of purchase. Unsubscribe at any time via the link in any email. See our Privacy and Terms.

← Previous phase

Permits

Next phase →

Construction