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The DFW ADU Feasibility Guide
A backyard home (an ADU — Accessory Dwelling Unit) can house a parent, an adult child, a guest, or bring rental income. But most of the money is lost before the build — on plans for a project that was never going to work. This guide is the homework that stops that, in plain language, from each city's own rules.
The 5 questions to answer before you spend anything
1 · Does my city even allow it?
Not every city permits an independent second home, and the ones that do call it different things — Backyard Cottage, ADU, Guest House, Garage Apartment. Some ban renting it out. Start here, because everything else is moot if the answer is no.
2 · How big can it legally be on MY lot?
Cities cap size by a formula tied to your lot size and your main home's floor area (e.g. "the lesser of 1,000 sq ft or 25% of your home"). The number you can build is rarely the number you imagined — check it before you fall in love with a floor plan.
3 · Will it physically fit — after setbacks and the front yard?
Legal max ≠ what fits. Setbacks, the required distance behind the main house, your driveway, and easements all eat into the buildable area. A big 2-story home on a small lot can pencil out on paper and still have nowhere to put the cottage.
4 · What will the WHOLE thing cost — not just the box?
The factory or shell price is the small part. Foundation, utilities, permits, site work, and delivery/crane are the rest. Budget the all-in number, not the sticker.
5 · What do the private rules say?
Your HOA and your deed (recorded restrictive covenants) can be stricter than the city — some prohibit a second unit outright or set a minimum size. The city won't tell you this; it's in your deed records. Confirm it before you buy or build.
Where the money actually goes
The single most common surprise: the home itself is roughly a third of the real cost. Site work — foundation, utility hookups, permits, driveway, delivery and crane set — is the bigger share. A cheap unit on a hard site becomes an expensive project.
Illustrative split, not a quote — the real ratio depends on your site (how far utilities and the nearest pole are, soil, access). Your Roadmap puts a real number on it.
The rules where you are
Every line below traces to the city's own published ordinance (dated and linked). This is a summary — your exact lot decides the rest.
Plano
Full Plano rules →Plano calls them Backyard Cottages — and thousands of lots qualify.
Lot size: Minimum 6,000 sq ft lot.
The catch most people miss: The owner-occupancy deed restriction: if you're an investor who won't live on the property, a Plano Backyard Cottage is not a rental play. For families housing a parent or adult child, it's ideal.
Source: City of Plano Backyard Cottage Fact Sheet · verified 2026-07-12
McKinney
Full McKinney rules →McKinney publishes its own ADU guide — a city that wants you to succeed.
Eligibility: Single-family residential zoning with room to meet regulations. Planned Development (PD) zones may not allow an ADU — address-specific check required.
The catch most people miss: PD zoning. A large share of newer McKinney neighborhoods sit in Planned Developments with their own rules — the city's general ADU rules may not apply to your address. This is exactly what our report checks first.
Source: Building an ADU in McKinney (official city guide) · verified 2026-07-12
Frisco
Full Frisco rules →Frisco allows guest houses and garage apartments — with one big string attached.
What's allowed: A Guest House (detached) or Garage Apartment (attached to a garage) as an incidental use on a single-family lot, per UDC §4.06.
The catch most people miss: The owner-occupancy-to-rent rule: rental income is only legal while you live in the main house. And Frisco HOAs are pervasive — deed restrictions can be stricter than the city.
Source: Frisco Unified Development Code §4.06 — Accessory Structure Standards · verified 2026-07-12
Denton
Full Denton rules →The CITY of Denton has some of the clearest ADU rules in North Texas. (This covers Denton city limits only — Denton-County suburbs like Flower Mound, Little Elm, and Lewisville each have their own rules.)
ADU size: Up to 800 sq ft or 75% of the main home's size — whichever is GREATER.
The catch most people miss: The design-compatibility rule surprises people: a visible ADU can't look like a shed dropped in the yard. Factory-built modular units can meet it — if you pick finishes deliberately, which is part of what we do.
Source: City of Denton — Accessory Dwelling Unit (ADU) · verified 2026-07-12
Lucas
Full Lucas rules →Lucas allows a backyard cottage on big acreage lots — but it can never be a rental.
Cottage size: Up to 900 sq ft by right. Up to 1,500 sq ft is possible with a Specific Use Permit — City Council approval, not guaranteed.
The catch most people miss: The no-rental rule is absolute. Most of our launch cities restrict rentals to owner-occupied properties — Lucas goes further and bans renting the cottage out at all, ever. This is the right city for a multigenerational family or guest suite, not an income property.
Source: City of Lucas Code of Ordinances — Ch. 14 Zoning, Div. 8 Accessory Buildings · verified 2026-07-18
Parker
Full Parker rules →Parker allows a cottage on acreage — but only for family, guests, or live-in help, never a tenant.
Lot size: At least 1 acre for an attached cottage, or a full 2 acres for a detached one — the strictest lot-size rule of any city we cover.
The catch most people miss: The rental ban is airtight, and the annual SUP renewal — required for BOTH attached and detached units — is unique among our cities — most places make you get one permit once; Parker makes you re-apply every year. This is a fit for a genuinely rural, multigenerational property, not a rental strategy.
Source: City of Parker, TX Code of Ordinances — Ch. 156 Zoning, §156.37(O) · verified 2026-07-18
The permit path, in order
- Confirm eligibility — city + zoning (watch for Planned-Development overlays and HOAs).
- Size & place it — apply the city's formula and setbacks to your actual lot.
- Plans — a model that fits the number and the rules (in most Texas cities a homeowner can pull their own permits).
- Permit submission — the city's portal, forms, fees, and reviews.
- Build & inspect — licensed trades where the law requires them; final inspection and sign-off.
On rural land instead?
If you own acreage in Collin, Denton, Wise, Parker, Grayson, Hunt, or Fannin County, the questions are different — septic, water, floodplain, and access. See the rural land guide →
Want these five answered for YOUR address?
Run the free check for your city's rules and your lot's public records, or get the Owner's ADU Roadmap — a paid, site-visited report that answers all five in writing.