How to actually pay for a casita in Arizona

The four real options

For a casita build in Arizona, the money almost always comes from one of these:

1. Home Equity Line of Credit (HELOC)
2. Cash-out refinance
3. Renovation loan (against after-completion value)
4. Construction-to-permanent loan

Each fits a different mix of equity, credit, rate environment, and appetite for paperwork.

1. HELOC — a second mortgage line you draw from

A HELOC is a revolving line secured by your home. In Arizona today most programs will lend up to 80–85% of your current home value minus your existing mortgage balance. Once the line is open, you draw as construction progresses and only pay interest on what you've actually drawn.

Good fit if:

• You have significant equity in your main home already.
• You don't want to touch your existing low-rate first mortgage.
• You want flexibility — draw only what you actually need.

Tradeoffs:

• Rate is variable. If rates move up during the build, so does your interest.
• The line eventually enters an amortization phase — payments jump.
• Total borrowing is capped by current equity, not the finished value.

2. Cash-out refinance

You refinance your existing mortgage into a new, larger one and pocket the difference as cash to fund the build. Fixed rate, one payment, done at closing.

Good fit if:

• Your current mortgage rate is already at or above today's market rate.
• You have plenty of equity and want a lump sum, not a line.
• You want the certainty of a fixed rate on the whole project.

Tradeoffs:

• If you have a low-rate mortgage from 2020–2021, refinancing usually costs more than it saves.
• You pay closing costs on the whole loan, not just the new money.
• Still capped by current appraised value.

3. Renovation loan (ARV — after-completion value)

This is the option most homeowners don't know exists. A renovation loan lends against what your property will be worth after the casita is built — up to roughly 90% ARV on some programs. That's a big deal, because adding a casita usually raises your appraised value.

Simple example: your home is worth $500,000 today. With a fully permitted 1,000 sq ft casita, the appraiser projects it at $650,000. A 90% ARV loan can lend against that projected $650,000, not the $500,000 you have today.

Good fit if:

• You don't have enough current equity to fund the build with a HELOC.
• The casita meaningfully raises your appraised value.
• You're okay with one consolidated loan instead of a line.

Tradeoffs:

• Underwriting is more involved — plans, contractor bids, and a "subject-to-completion" appraisal.
• Funds are released in draws, not all at once.
• Not every lender offers ARV renovation loans — this is a specialty product.

4. Construction-to-permanent loan

One loan, two phases. During construction, it funds the build in draws tied to inspection milestones (foundation, framing, dry-in, mechanicals, finish, final). When construction is complete, it automatically converts to a standard fixed-rate mortgage — no second closing, no requalifying.

Good fit if:

• You're building a bigger project or a full ground-up structure.
• You want one closing and predictable long-term payments.
• You have detailed plans and a licensed GC on contract.

Tradeoffs:

• Most paperwork up front. Expect 4–8 weeks to close before construction can start.
• You typically make interest-only payments during construction, then full P&I after conversion.

How to actually decide

The right answer depends on three things:

• Your current equity: if you have plenty, a HELOC is often the simplest.
• Your current mortgage rate: a 3% first mortgage is worth protecting — don't refinance it lightly.
• The finished project's projected value: if the casita adds significant value, an ARV renovation loan may unlock more usable funds than any current-value product.

I run these numbers for Arizona homeowners for free. Fifteen minutes on the phone and you'll know which product fits your lot, your equity, and your goals. There's no cost, and I'll tell you if the answer is "wait a year."

Frequently asked questions