The Utah ADU buyer's guide
Buying a home with an ADU in Utah
An accessory dwelling unit, or ADU, is a second self-contained living space with its own entrance and kitchen, built inside the home or standing alone in the yard. Buying a home that has one, or has room to add one, can be a smart move. It also adds three questions a plain purchase does not: is the unit legal, will its rent help you qualify, and what do you check before you write the offer.
This is the buyer's version. For the layout options and living side by side, see multi-generational homes, part of the moving-up hub.
On this page
The short answer
Buying with an ADU, the honest version
Here is the whole thing in a paragraph. An accessory dwelling unit is a second, self-contained place to live on the same property: its own entrance, its own kitchen, its own bath. Sometimes it is finished space inside the house, like a lower-level apartment. Sometimes it is a casita or cottage standing on its own in the yard. Buying a home that already has one, or that has the room to add one later, gives you a flexible second space you can rent for long-term income, use as an office or a guest room, or simply leave alone. What you plan to do with it decides which questions matter most.
A second unit does come with strings, and this is where buyers get surprised. Three things decide whether an ADU is an asset or a headache: whether the unit is legal in the eyes of the city, whether a lender will let its rent help you qualify to buy, and whether it was permitted and built to code. Get those three right before you write the offer and the ADU is a real advantage. Skip them, and an unpermitted or non-conforming unit becomes your problem the day you close, not the seller's. This page walks all three. For the layout options themselves, and the case for two households under one roof, I cover those on multi-generational homes.
Which kind you are buying
Three kinds of ADU, and why the difference matters
The word ADU covers a few very different things, and the difference is not decoration. It decides which rules apply, because Utah protects one kind statewide and leaves the rest to your city.
Internal ADU
A unit built inside the home's existing footprint, like a finished lower level with its own kitchen and door. This is the kind Utah protects. In most residential areas a city has to allow one for a long-term rental, without a special hearing.
Attached ADU
A unit joined to the house, often a converted space over an attached garage or a wing behind its own entrance. Whether it counts as internal, and earns the state protection, depends on how it ties into the home. Ask the city how they classify it.
Detached ADU or casita
A stand-alone building in the yard with its own kitchen and bath. The state internal-ADU rule does not reach it, so whether you can have or use one is entirely the city or county call, and the answer changes from town to town.
Utah's internal-ADU law
What the state guarantees, and what your city still controls
In 2021 the Utah Legislature passed House Bill 82, and it changed the ground under this whole topic. The law made an internal accessory dwelling unit a permitted use in most areas zoned for homes, which means a city generally has to allow one and cannot send you through a discretionary hearing to get it. There are conditions built in: the unit has to sit inside a single-family home, it is meant for a long-term rental of thirty days or more, and it is one unit, not several. That is the statewide floor, and it is a real one.
On top of that floor, your city keeps a set of controls, and this is why two towns twenty minutes apart can give you different answers. A city can require you to live in the main home as your primary residence, can ask for an extra parking space, can require a rental license, can keep an ADU off the smallest lots, and can map out a limited share of its residential land, up to about a quarter of it, where the rule does not apply. And the whole protection is for internal units only. A detached casita or backyard cottage sits outside the state law and lives entirely on the local ordinance, so a plan that works in one city can be a flat no in the next. Anytime money or a dispute rides on it, the zoning questions belong with the city planning office and, where needed, an attorney.
Can the rent help you buy
When the unit's rent can help you qualify
Here is the part that makes an ADU more than a nice feature. When you buy a home to live in and it has a legal accessory unit, a lender may let some of that unit's rent count toward what you can afford. It is not automatic, and it is not the whole rent. The lender leans on an appraiser's opinion of what the unit would rent for in that market, and often a signed lease, then allows a portion of it to help your numbers. How much counts, and whether it counts at all, depends on the loan program and your own file. The rules here have opened up in recent years, which is good news for buyers, but they are still the lender's to apply, not something to size up from a guide.
This is where being both an agent and a lender earns its keep. I can look at a home's ADU and your qualifying picture together, so you find out early whether the rent actually helps you buy, before you fall for a place while counting on income that may not count. I take one role on any given purchase and never both at once, you are always free to use any lender you like, and what you finally qualify for is a lender's call on your situation. The tax side of rental income is real too, and that part belongs with a CPA.
One honest caution. If the unit is not legal, or the appraiser cannot support a rent for it, that income may simply not be there when the loan is written, and a plan built on it can fall apart at the worst moment. So the money question and the legal question are really the same question, which is why the next step is verifying the unit before you commit. If renting the ADU while you live in the main home is the real plan, that is its own strategy, and I walk it on house hacking in Utah.
Verify it before you offer
Six checks, before you write the offer
An ADU is only worth what it can legally do. Run these while you still have room to walk away, inside the offer's due-diligence window, not after you own it. Most of it is a phone call to the city and a careful read of the file.
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Read what the listing actually claims
Sellers describe a basement apartment or casita in glowing terms that are not the same thing as legal. Get the claim in writing, then treat every word of it as something to verify, not to trust.
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Confirm the zoning and what the city allows
Ask the city or county planning office what the parcel allows for a second unit, and have them separate internal from detached, because the answers are different. The listing agent can point you there, but confirm it at the source. The full zoning walkthrough.
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Pull the permit history
Ask whether the unit was permitted and whether any sleeping rooms have legal egress. An unpermitted conversion is the single most common ADU surprise, and it turns into your liability, your cost, and sometimes your teardown, the moment you close.
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Check owner-occupancy and licensing
If your plan is to rent the unit, confirm whether the city requires you to live in the main home and whether it wants a rental license. A rule you did not know about can end a rental plan fast.
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Sort long-term from short-term
The state protection is for rentals of thirty days or more. Nightly rental is a separate world with its own local rules, and many cities limit or ban it. If a short stay is ever the idea, read those rules closely first. Utah short-term rental rules.
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Tell your lender early, and build it into the offer
If the ADU income matters to your loan, loop the lender in before the appraisal so market rent gets captured, and write the whole question into your due-diligence deadline so you can walk away clean if it does not hold up.
Buying it with me
One person who can read the permit and the financing
Here is the part a guide cannot do for you. An ADU sits right where the property rules and the loan rules meet, and it helps to have one person who can see both at once.
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Twenty years living in Southern Utah. I have lived here more than twenty years. I help buyers across Iron and Washington counties tell a real, rentable accessory unit from one that only looks legal on a listing.
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Agent and lender, one picture. I am licensed in both, so I can tell you early whether a home's ADU is likely legal and whether its rent can help you qualify. I take one role on any purchase, never both at once.
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The honest read, not the hopeful one. If the unit was never permitted or the income will not count, I would rather tell you before you offer than let you find out at closing. A quiet no now beats an expensive surprise later.
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Local in the south, connected statewide. In Southern Utah I handle the search myself. Anywhere else in Utah, I connect you with a partner agent I trust in your area and stay involved.
Questions, answered
What buyers ask about homes with an ADU
An ADU, or accessory dwelling unit, is a second self-contained place to live on the same property, with its own entrance, kitchen, and bath. It can be internal, meaning it is built inside the home like a lower-level apartment, or detached, meaning it stands on its own in the yard like a casita. When you buy a home with one, the unit can be rented for income, used as an office or guest space, or left alone. What matters most is whether it is legal and permitted, which you confirm before you write the offer.
Internal ADUs are broadly legal. A 2021 state law, House Bill 82, made an internal accessory dwelling unit a permitted use in most residential areas, so a city generally has to allow one inside a single-family home for a long-term rental of thirty days or more. Cities still control the details, like whether you must live in the main home, parking, a rental license, and the smallest lots, and they can exempt a limited share of their residential land. Detached ADUs are not covered by that law and are entirely up to the city or county, so always confirm the rule for the specific parcel.
Often some of it, yes. When you buy a home to live in that has a legal accessory unit, a lender may let a portion of the unit's rent count toward what you can afford, usually based on an appraiser's opinion of market rent and often a signed lease. How much counts, and whether it counts at all, depends on the loan program and your own file, so it is a lender's call, not something to estimate from a guide. The honest catch is that the income only counts if the unit is legal, which is one more reason to verify it early.
It becomes your problem at closing, not the seller's. An unpermitted conversion can mean the unit is not legal to rent, was not built to code, or has sleeping rooms without proper egress, and the city can require you to fix it or remove it. A lender also will not count income from a unit that is not legal. Before you offer, pull the permit history and ask the city planning office directly, and build the answer into your due-diligence deadline so you can walk away clean if it does not hold up.
No, and this is where buyers get caught. Utah's internal-ADU law covers units built inside the home, not stand-alone buildings in the yard. Whether you can have or use a detached casita or cottage is entirely the city or county decision, and it changes from town to town. A backyard unit that is fine in one city can be flatly not allowed in the next, so never assume a detached unit is legal just because the home already has one. Confirm it with the local planning office for that exact address.
Both can work, and the right answer depends on the home and your timing. Buying a home that already has a legal, permitted unit means the space is done, and if it is legal, its rent may help you qualify right away. Buying a home with room to add an internal unit later gives you a project and more control, but you take on the permitting, the cost, and the time, and you confirm the city allows it first. Either way, the legal question comes before the money question, so start there.
Keep exploring
Thinking about a home with an ADU?
I am Scott Buehler, a licensed Utah real estate agent and mortgage lender, and I have helped buyers across Southern Utah tell a real, rentable accessory unit from one that only looks the part on a listing. Tell me the home or the area and what you want the unit to do, and I will help you sort what is legal, what a lender will count, and what to verify before you write anything. The loan specifics stay with a lender, always. No pressure, and no obligation.
Not in Southern Utah? I will connect you with a partner agent I trust in your area, and stay involved.