Home features · casitas and guest houses
Homes with casitas in Arizona: the rules, the cities, and the financing
A casita can mean a guest room with a bath or a full second home on the lot. Here's what Arizona law now allows, how Phoenix and Mesa apply it, and how lenders treat it.
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Can I have a casita on my lot in Arizona?
Quick answer: In most cases, yes. A.R.S. §9-461.18 requires Arizona cities over 75,000 people to allow at least one attached and one detached accessory dwelling unit on single-family lots, and A.R.S. §11-810.01 sets similar rules for counties. HOA covenants can still restrict them, so check the CC&Rs before you buy.
Source: Arizona Revised Statutes §9-461.18 and §11-810.01. Last updated .
What a "casita" is, legally
"Casita" is a listing word, not a legal one. Arizona's ADU law defines an accessory dwelling unit as a self-contained living unit on the same lot as a single-family home, with its own sleeping and sanitation facilities, and it may include a kitchen. The City of Phoenix says ADUs are "often referred to as guest houses, casitas, or granny flats." A detached bedroom-and-bath "casita" without a kitchen may be permitted as a guest room or accessory structure instead. Ask the seller for the permits.
What Arizona's ADU law requires of cities
For cities and towns with more than 75,000 people, A.R.S. §9-461.18 says the city must allow, on any lot where a single-family home is allowed:
- At least one attached and one detached ADU as a permitted use, plus a second detached ADU on lots of one acre or more if one unit is restricted-affordable.
- An ADU of at least 75% of the home's floor area or 1,000 square feet, whichever is less.
- Side and rear setbacks of no more than 5 feet.
The city may not ban renting the ADU long-term (90 days or more), require the occupant to be related to the owner, require extra parking, require matching design, or require fire sprinklers or a commercial building code. If a city didn't adopt rules by January 1, 2025, ADUs are allowed without limits. Exceptions include tribal land and areas near military airports or noisy airports. Private covenants, including HOA CC&Rs, are not overridden.
A.R.S. §11-810.01 applies similar rules to counties, with a January 1, 2026 deadline, a second detached ADU allowed on lots of an acre or more, and permission to require adequately sized septic where there's no sewer.
City by city
| City | Census population (ACS 2020–2024) | Over the law's 75,000 threshold? | Local notes |
|---|---|---|---|
| Phoenix | 1,642,323 | Yes | City Council approved ordinance changes in late 2024. When a lot has one single-family home, two ADUs are permitted, and a third may be permitted in some cases. The city offers free, already-reviewed ADU Standard Plans to residents, from a 2024 AIA design competition. |
| Mesa | 511,764 | Yes | One attached and one detached ADU on any lot with a single residence; an extra detached ADU on lots over an acre if one unit is restricted-affordable (up to 80% of area median income). Size up to 1,000 sq ft or 75% of habitable floor area, whichever is less; 5-foot side and rear setbacks. RVs, trailers, and tiny homes on wheels can't be ADUs. |
| Gilbert | 280,262 | Yes | State minimums apply; check the town's code and your HOA. |
| Chandler | 280,136 | Yes | State minimums apply; check the city's code and your HOA. |
| Scottsdale | 243,821 | Yes | State minimums apply; check the city's code and your HOA. |
| Queen Creek | 71,867 | Not by this ACS estimate | The ACS 5-year estimate is under 75,000. Check the town's current rules directly. |
Population: U.S. Census Bureau, ACS 2020–2024 5-year (B01003). The statute doesn't say which population figure applies, so confirm with each city. Phoenix and Mesa notes from each city's ADU page, retrieved October 4, 2026.
How a casita affects the loan
- FHA can count casita rent. HUD Mortgagee Letter 2023-17 (effective immediately on October 16, 2023) lets FHA lenders count rental income from an ADU on a one-unit property. With no rental history, the lender uses 75% of the lesser of the appraiser's market rent or the lease, and ADU income can't exceed 30% of the income used to qualify.
- Appraisal. The same letter sets how appraisers report ADU market rent. A permitted, self-contained unit is easier to value than an unpermitted conversion.
- Taxes and insurance. A larger structure can raise the home's value and insurance cost. A payment-first search shows each home's own tax bill, so compare full monthly cost, not price.
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Opens the MABLS home search. Payments shown there are estimates to help you search, not a loan offer or rate quote.
- Make it exact with Pam. Get pre-qualified with Pam Messina. Once you're pre-qualified, Pam can update the maximum monthly payment and total funds to close in your MABLS search, so results match what you actually qualify for. If you'd like, she can also give you a free, no-obligation introduction to a real estate professional so you can start touring homes.Get pre-qualified with Pam (opens in a new tab)
Applications are handled by Pam Messina, NMLS #245626, Rebel Rate Mortgage, Inc. (NMLS #2571369).
Opens Rebel Rate Mortgage's secure online application (my1003app.com) in a new tab. Pre-qualification isn't a loan approval or a commitment to lend; approval depends on underwriting, verification of your information, and the property.
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Ask Pam how a casita or guest house affects financing for a specific home: whether rent can count, and what the appraisal needs to show.
Related: Power Ranch, Gilbert · 55-and-over communities · Arizona FHA loans · All home feature guides
Data as of October 4, 2026. Figures are cited to the public sources listed below. General information for Arizona home shoppers, not a loan offer, rate quote, or commitment to lend.
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Sources
- Arizona Revised Statutes §9-461.18, accessory dwelling units in municipalities (retrieved October 4, 2026)
- Arizona Revised Statutes §11-810.01, accessory dwelling units in counties (retrieved October 4, 2026)
- City of Phoenix, Accessory Dwelling Units (retrieved October 4, 2026)
- City of Mesa, Accessory Dwelling Units (ADUs) FAQ (retrieved October 4, 2026)
- U.S. Department of Housing and Urban Development, Mortgagee Letter 2023-17, Accessory Dwelling Units (dated October 16, 2023; retrieved October 4, 2026)
- U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates: B25077 (median home value), B25103 (median real estate taxes paid), B25088 (median owner costs with a mortgage), B08013/B08303 (mean travel time to work), B25003 (owner-occupied share), B01003 (population) (retrieved October 4, 2026)
Frequently asked questions
What is a casita in Arizona?
A casita is a small guest house or suite, usually detached. Legally it may be an accessory dwelling unit (with its own sleeping and sanitation facilities) or a guest room without a kitchen. Phoenix says ADUs are often called guest houses, casitas, or granny flats.
Can I rent out my casita in Arizona?
Under A.R.S. §9-461.18, cities over 75,000 people can't ban long-term rental (90 days or more) of an ADU. HOA covenants can still restrict rentals, so read the CC&Rs.
How big can a casita be in Mesa?
Mesa allows an ADU up to 1,000 square feet or 75% of the home's habitable floor area, whichever is less, with 5-foot side and rear setbacks.
Can my HOA ban a casita?
Possibly. Arizona's ADU laws limit what cities and counties can require but don't override private covenants between owners, so HOA CC&Rs can still restrict ADUs.
Can casita rent help me qualify for an FHA loan?
It can. HUD Mortgagee Letter 2023-17 lets lenders count ADU rental income on a one-unit property, using 75% of the lesser of market rent or the lease, capped at 30% of qualifying income.
Are multigenerational homes the same as homes with casitas?
Builders use multigenerational for floor plans with a separate suite, which may or may not be a legal ADU. Ask whether the suite has its own entrance, kitchen, and permits.