The Ultimate Guide to Financing an ADU in Florida

ADU construction in Florida costs $80,000–$310,000 — more than most homeowners have in cash. The five financing paths below cover the full range from HELOC to ADU-specific credit union loans. Key question for each: can you count projected rental income toward your qualification? The answer changes your borrowing capacity significantly.

HELOC: The Most Common Florida ADU Financing Tool

A Home Equity Line of Credit is the most used ADU financing method for Florida homeowners with existing equity. You borrow against your home's appraised value above your current mortgage balance — drawn as needed during construction rather than as a lump sum at close.

Current rates: 7–9% variable (Prime + 0.5–2.5%), as of early 2026. Rates adjust with the prime rate — downward movement could reduce your cost; upward movement adds payment risk.

How the math works: If your home is worth $400,000 and you owe $200,000, you have $200,000 in equity. Florida lenders typically cap HELOC combined loan-to-value (CLTV) at 80–85% of appraised value. At 80%: $400,000 × 80% = $320,000 − $200,000 existing mortgage = $120,000 available HELOC. At 85%: $340,000 − $200,000 = $140,000 available.

Best for: Homeowners with 25%+ equity, a firm ADU budget, and comfort with variable-rate exposure. Interest-only payment during the 10-year draw period keeps monthly cash outlay low while construction is underway.

Florida-specific note: Florida's homestead exemption does not affect HELOC availability — your primary residence can be pledged as HELOC collateral even with homestead status. However, Florida has specific homestead protection laws that affect foreclosure risk — consult a Florida real estate attorney if you have concerns about pledging homestead equity.

Cash-Out Refinance

Cash-out refinancing replaces your existing mortgage with a new, larger mortgage and gives you the difference as a lump sum to fund ADU construction.

Current rates: 6.5–7.5% fixed (30-year), as of early 2026. Unlike a HELOC, a cash-out refi locks your rate for the life of the loan — no variable rate exposure.

When it makes sense: If your current mortgage rate is at or above current refinance rates (many Florida homeowners refinanced at sub-4% in 2020–2021 — for those borrowers, a cash-out refi at 7% is expensive), or if you want payment certainty rather than a variable-rate draw. If your existing rate is already above 6.5%, cash-out refinancing is worth modeling seriously.

Break-even calculation: A $150,000 cash-out refi at 7.0% over 30 years adds $997/month to your payment. If your ADU generates $1,500/month in rent (75% of which = $1,125 that Fannie Mae will count toward qualification), the ADU covers its own debt service with margin. Run this math with your actual numbers before deciding.

Closing costs: Cash-out refis carry full closing costs — typically $4,000–$8,000 in Florida. Factor this into your total ADU project cost.

Construction-to-Permanent Loan

A construction-to-permanent (C-to-P) loan covers both the construction phase (money drawn as work is completed and inspected) and the permanent mortgage (converts automatically at completion — no second closing). This is the cleanest structure for large ADU projects ($150,000+).

Rates: Typically 0.25–0.75% above standard mortgage rates during construction, converting to standard rates at close. Expect 7.0–8.0% during the construction phase in early 2026.

Requirements: Full construction plans and specifications, a licensed general contractor with a signed contract and active license, and an appraisal of the completed project. The construction budget is reviewed in detail by the lender — any significant changes require approval.

Disbursement: Funds are held in escrow and released in draws tied to inspection milestones (foundation, framing, rough-in, insulation, drywall, final). This protects you from paying a contractor in full before work is complete.

Lenders offering C-to-P in Florida: Fifth Third Bank, Regions Bank, Wells Fargo, and most major Florida credit unions. Smaller community banks in each metro market often have competitive local C-to-P programs worth comparing.

Fannie Mae HomeStyle Renovation Loan

The HomeStyle loan is Fannie Mae's renovation product — it finances construction or rehabilitation costs into a purchase or refinance based on the "as-completed" appraised value. This is especially powerful if you're buying a home and want to fund ADU construction in the same transaction.

Key advantage: You borrow against what the property will be worth after ADU construction, not what it's worth today. If your home appraises at $350,000 today but will appraise at $450,000 with the ADU complete, the HomeStyle loan can be based on $450,000.

Loan limits: Must stay within Fannie Mae conforming limits — $766,550 in most Florida counties, higher in high-cost areas (Miami-Dade, Palm Beach, Monroe). For South Florida's HVHZ markets where ADU construction costs are higher, this higher limit is important.

Process: Requires a licensed contractor, approved plans, and an appraiser who will generate a "subject to" appraisal (valuing the property assuming construction is complete). Funds released in draws with lender-approved inspections, similar to a C-to-P.

ADU-Specific Loan Programs from Florida Credit Unions

Several Florida credit unions have introduced products that underwrite specifically for ADU construction, including counting projected rental income in the debt-to-income calculation. These programs are not widely advertised — call the credit union directly and ask for their ADU or accessory dwelling unit loan product.

Florida credit unions with ADU loan history:

• Suncoast Credit Union — Tampa Bay area, strong ADU lending history
• Space Coast Credit Union — Central and East Florida
• Achieva Credit Union — Tampa Bay
• VyStar Credit Union — Jacksonville area, largest in Northeast Florida
• Grow Financial Federal Credit Union — Tampa

National ADU-focused lenders like RenoFi have also expanded into Florida. RenoFi offers renovation loans based on after-renovation value — similar in concept to HomeStyle but available through a broader lender network.

Counting Rental Income Toward Qualification

This is the question that changes the math for most ADU borrowers:

• New construction, no rental history: Fannie Mae Guidelines B3-3.1-08 allow lenders to count 75% of projected ADU rental income if the appraiser provides a market rent estimate and the ADU will be a livable, permitted space. This requires the appraisal to include a rent schedule.
• Existing ADU with lease and tax history: With a signed lease and 12 months of Schedule E rental income on your tax returns, lenders count 75% of actual rents received. This is the strongest documentation scenario.
• Investment property financing: If you don't occupy the primary residence, the entire property (primary + ADU) is treated as investment property, requiring 20–25% down payment and higher rates.

Example: An ADU generating $1,600/month projected rent × 75% = $1,200 added to qualifying income. At a 40% debt-to-income ratio, $1,200/month in additional qualifying income supports roughly $168,000 in additional loan capacity (at 7% / 30 years). For a project in the $150,000–$200,000 range, this income credit can be the difference between qualifying and not.

Frequently Asked Questions

What credit score do I need to finance an ADU in Florida?

Conventional financing (cash-out refi, HELOC, HomeStyle) requires a minimum 620–640 FICO score, with materially better rates at 720+. Construction-to-permanent loans typically require 680+ due to additional construction risk. Credit union ADU-specific programs may have more flexible underwriting — ask about their minimum requirements directly.

Can I use a personal loan to build an ADU in Florida?

Technically yes, but the economics are poor. Personal loan rates in 2026 run 8–18% vs. 6.5–7.5% for home-secured products. On a $120,000 ADU project, the extra 3–5% annual interest costs $3,600–$6,000/year. Personal loans work only for very small ADU projects (garage conversions under $60,000) where the faster approval timeline justifies the rate premium.

Does ADU construction increase my property taxes in Florida?

Yes. Adding a permitted ADU increases your property's assessed value, which raises your annual tax bill. Florida's homestead exemption caps annual assessment increases at 3% for homesteaded properties — but adding a new structure may trigger a partial reassessment of the improvement value. In Miami-Dade, homeowners report 15–25% property tax increases after ADU construction. Contact your county Property Appraiser for a rough estimate before finalizing your budget.

Can I finance an ADU construction with a 203(k) loan?

FHA 203(k) loans finance rehabilitation of existing structures but are not typically used for new ADU construction on a separate lot or building. The Standard 203(k) requires work to be done to the existing home. Fannie Mae HomeStyle is generally the better product for ADU construction financing and has higher loan limits in most Florida markets.