Quick answer: When parents fund a backyard cottage on an adult child's property, the construction is genuinely the easy part — a fixed price, a permit path, 10–16 months, done. The part families skip is the part that causes trouble years later: money put into land you don't own becomes, by default, a gift to the landowner. Washington families generally handle it one of five ways — a documented gift, a formal family loan, co-ownership on the title, a written occupancy agreement, or (unique to Washington's new framework) condominium-form ownership where the DADU can be owned separately. None of them is wrong; the mistake is picking one by accident. Below: the five structures in plain English, the five questions to settle at the kitchen table before design starts, and where the builder's job ends and the attorney's begins. This is planning context, not legal or tax advice — structure the paperwork with an estate or real-estate attorney and a tax professional.
Key facts
- The default nobody chooses: absent paperwork, money a parent puts into a child's property generally benefits the property's owner — the person on the title. If that's the intent, document it; if it isn't, structure it.
- The sums are real: a typical detached DADU here runs $250,000–$450,000 ($185,000–$320,000 for standard cottages; conversions from $85,000) — the size of inheritance conversations, not birthday gifts.
- Five common structures: documented gift · formal intra-family loan · co-ownership on title · written occupancy/life-use agreement · condominium-form separate ownership (newly practical under Washington's 2026 ADU framework).
- Annual and lifetime gift-reporting rules exist and change — the current limits are a tax-professional question, not a blog-number question.
- Washington's 2026 rules allow two ADUs per lot in urban growth areas with no owner-occupancy requirement, and permit condo-form separate sale of a DADU — which makes "the parents own their cottage" a real, titled option, not a handshake.
- Whatever the structure, the build contract stays clean: one owner-side signer, a fixed price with written exclusions, and lien releases protecting the property — we handle that side on all 93+ of our ADUs.
The conversation families skip (and pay for later)
Here's the pattern we see: everyone agrees the cottage is a great idea, the parents offer to fund it, design starts, and the ownership question gets postponed because raising it feels like distrust. Then life does what life does — a sibling asks why the family money sits inside one child's house, a parent needs long-term care and the state asks where assets went, the homeowners divorce or sell, or the parents pass and the will says nothing about a $350,000 cottage. None of these are rare, and all of them are cheap to handle before construction and expensive after. The kitchen-table meeting is the real foundation pour.
The five structures, in plain English
(What each one is and what it solves — your attorney tailors the details.)
| Structure | In one sentence | What it solves |
|---|---|---|
| Documented gift | Parents fund the build; paperwork records it as a gift to the homeowner | Simplicity; clean title; sibling clarity via the estate plan |
| Formal family loan | Parents lend the cost, with a written note and terms | Keeps value on the parents' balance sheet; repayment or forgiveness stays flexible |
| Co-ownership on title | Parents are added to the property's title for an agreed share | Parents hold real equity, not a promise |
| Occupancy / life-use agreement | Homeowner owns everything; parents hold a written right to live there | Security for the parents without changing title |
| Condo-form separate ownership | The DADU becomes its own titled unit the parents own outright | The cleanest "it's their cottage" — newly practical in Washington; details in our separate-sale guide |
Two honest notes. First, each structure touches taxes, estate plans, and — where long-term care may be ahead — asset-timing rules; current thresholds and look-back rules are exactly what you pay a professional an hour to confirm. Second, the right answer often isn't the "best" structure on paper — it's the one every sibling heard explained at the same table. If the plan involves borrowing rather than parent cash, our DADU financing guide covers the lender side; what a cottage does to the property's resale value is worth reading alongside it.
The five questions to settle before design starts
(1) Whose money is it, legally — gift, loan, or investment? Say the word out loud and write it down. (2) What happens if the house sells? Do parents get repaid, a share, or nothing — and does everyone know? (3) What happens when the parents no longer live there? Long-term rental at market ($1,600–$2,800/mo around here), family use, or sale — decided now, calmly. (4) What do the siblings know? The cottage that surprises the family at the estate reading is the one that ends up in a dispute. (5) Who signs the construction contract? One owner-side signer keeps permits, payments, and lien releases clean — however the family shares costs behind the scenes.
Bring both generations: free site evaluation, fixed price, and a lot check in 60 seconds first. Or call (253) 332-9333.
Where our job ends and the attorney's begins
We're builders, and the line is bright: we handle feasibility, design, permits, fixed-price construction, and the lien-release paper trail that protects the property. The ownership structure — title, notes, occupancy agreements, condo formation — belongs to an estate or real-estate attorney, and the tax treatment to a CPA. What we can do is make their job easy: a clean fixed-price contract, documented payments, and a cottage designed for the long game (step-free entry, wider doorways, full kitchen and laundry — the features covered in our aging-parents guide) so the unit serves whoever lives in it across the decades the paperwork now contemplates.
Start with the ground truth
Before any of the five structures matters, one question comes first: does the lot even qualify? Run your address through Analyze My Lot — zoning, lot size, and buildable area in about 60 seconds, free. Then bring both generations to the free site evaluation: we'll walk the yard, confirm the utility path, and hand you a fixed price the whole family can plan around. Call (253) 332-9333.
Frequently Asked Questions
If my parents pay for an ADU on my property, who owns it?
By default, the property owner — that's you, because the cottage attaches to your land and title. If the family intends anything else (equity, repayment, separate ownership), it has to be structured deliberately: a documented gift, a loan, co-ownership, an occupancy agreement, or condo-form title. An attorney formalizes it; the mistake is leaving it to default.
Can my parents legally own the ADU itself in Washington?
Washington's 2026 framework permits condominium-form ownership, where a DADU becomes its own titled unit — so genuinely separate ownership is now a real option rather than a workaround. It takes legal setup; our separate-sale guide covers how it works.
Is money from parents for an ADU considered a gift?
Often, yes — and gift-reporting rules with annual and lifetime limits apply and change over time. Whether to structure it as a gift, a documented loan, or an equity share is exactly the one-hour conversation to have with a tax professional before construction starts.
What happens to the ADU if I sell my house?
Unless the family structured otherwise, the cottage sells with the property as one asset. If parents expect repayment or a share of proceeds, that expectation needs to exist on paper before it needs to exist in a closing statement.
Should the ADU be discussed in my parents' estate plan?
If parent money built it — yes. A few lines in the estate plan explaining the intent (gift to one child, loan to be settled, shared asset) is the cheapest sibling-dispute insurance a family can buy.
Who should sign the construction contract if my parents are paying?
Keep it clean: the property owner signs, one decision-maker runs the project, and the family's money arrangement lives in its own documents. That keeps permits, payments, and lien releases simple — however costs are shared behind the scenes.
Related guides: an ADU for your aging parents, DADU financing in 2026, selling a DADU separately in Washington, and what an ADU does to your home's value. Ready to price it? Book a free site evaluation or call (253) 332-9333. This is planning context, not legal or tax advice — structure the paperwork with an estate or real-estate attorney and a tax professional.