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Yes, you can start an ADU before the full cost is sitting in your bank account, but “pay later” means moving payments to a later date, not avoiding them. Five levers do the moving: promotional financing, staged billing from the builder, interest-only HELOC draws, construction-loan interest during the build, and rent from the finished unit.
Each lever changes when money leaves your account, not what the ADU costs, and most add interest while you wait. Below is how each one works and what to watch so a deferred payment does not become a surprise. For a side-by-side view of every loan type, start with our overview of ways to finance an ADU in Washington.
What “Pay Later” Actually Means on a Construction Project
In retail, “buy now, pay later” means a short installment plan on something you take home today. A backyard cottage is different: you pay for it as it gets built, and the bills arrive in a sequence.
That sequence is the opportunity. If the money for each stage is available when that stage is due, you never need the whole budget at once. Deferral, in an ADU context, is really about three things: shrinking what you must pay up front, keeping monthly payments low while nothing earns income, and bridging the months until the new unit pays some of its own way.
It is not free money. Whoever lends you the time charges for it, either through interest, through a higher rate after an introductory period, or through fees. The goal is to defer on purpose and know the price of each month you buy.
Lever 1: Promotional Financing for Part of the Budget
Promotional financing offers a reduced or introductory rate for a limited window, after which a standard rate applies to whatever balance remains. For an ADU, it works best on a defined slice of the project rather than the whole build: finish upgrades, appliances, a deck or landscaping around the new unit, or a gap at the end of a larger loan.
The deferral value comes from the introductory window. If you can repay the promotional balance before that window closes, you have effectively pushed part of the cost into the future at low cost. If you cannot, the balance moves to the standard rate, which is typically much higher than a home-equity product. Current offers and eligibility from United Signature’s financing partner are listed on the ADU financing page. The question of what to do as a promotional period approaches its end deserves its own planning, and we cover it in a later article.
Lever 2: Paying the Builder as Each Trade Finishes
The simplest form of deferral is built into the contract. United Signature takes a deposit at signing to cover design and the ordering of materials, and after construction starts, it bills as each trade is completed and verified, as described in the company FAQ.
Foundation work is paid when the foundation is done, framing when the framing is done, and so on, so your cash or credit line only has to keep pace with the work. Money can stay invested or untouched until the matching invoice arrives. How phased payments are scheduled, verified and documented on an ADU is a topic of its own, which a later article in this series covers in detail.
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Lever 3: The Interest-Only Window of a Home Equity Line
Many HELOCs have a draw period during which the minimum payment covers interest only, and only on the amount you have actually drawn. For an ADU, that creates a natural ramp: early in the build, when little has been drawn, the payment is small, and it grows as the cottage takes shape.
The trade-off is that interest-only payments do not reduce the balance. When the draw period ends, principal payments begin and the monthly amount rises, sometimes sharply. Most HELOC rates are also variable. Treat the interest-only phase as breathing room during construction and early occupancy, not as a long-term payment level. Sizing the line, the appraisal and the switch from draw to repayment get their own article later.
Lever 4: Construction-Loan Interest While the Unit Goes Up
With a construction loan, the lender pays out in stages, and while the cottage is going up you typically owe only interest on the portion already released. Principal enters the picture after completion, once the loan becomes a regular mortgage or is replaced by other financing.
For a homeowner, that means the heaviest payments line up with the period when the ADU can actually be occupied. The price of that structure is more paperwork, lender inspections before each draw, and a lender that must approve the timing of every payout. How draws, lender inspections and conversion work on a backyard unit is the subject of a separate article in this series.
Lever 5: Letting Future Rent Carry the Payments
If the ADU will be rented, the tenant’s rent can eventually cover much of the financing cost. That is a real form of deferral: you carry the payments for a period, and then the unit starts contributing.
The weak point is the gap. Rent does not start until the unit passes final inspection, is furnished or cleaned, is listed and is leased. Plan to cover payments from your own income for that whole gap, plus a cushion for a slow leasing month or a vacancy later. Our guide to renting an ADU in Seattle walks through what it takes to get a unit earning. Whether a lender will count projected rent when you apply is a separate question, and it depends heavily on the lender and the loan product.
Where D.E.P.P. Fits, and Where It Does Not
United Signature also offers D.E.P.P., the Deferred Equity Payment Program. It is a genuine pay-at-closing arrangement, but it is built for a specific situation: a homeowner who is preparing a house for sale and wants pre-sale renovations such as kitchen and bath updates, flooring, paint or exterior work.
Under the program, the owner makes a modest initial payment, the renovations are completed, the home is listed, and the remaining balance is paid from the sale proceeds at closing. Qualification rests on the equity available at sale, and the program has its own repayment window and charges on balances not repaid on time, so read the current terms on the D.E.P.P. program page.
The program page describes pre-sale renovations for sellers. It does not describe ADU construction, and an ADU is usually built by owners who plan to keep the property and benefit from the unit for years. If you are selling and want to improve the house first, D.E.P.P. is worth a conversation. If you are building a backyard cottage to keep, rely on the levers above and ask United Signature directly whether any deferred-payment option applies to your project.
The Costs That Keep Running While You Defer
Interest Starts With the First Dollar Borrowed
Every lever except staged billing and rent involves borrowed money, and interest begins accruing as soon as it is drawn. Deferring principal means paying interest on a larger balance for longer.
Variable Rates Can Move Mid-Project
HELOCs and some construction loans carry variable rates. A payment that looked comfortable at the start of design can be higher by the time the unit is finished.
Overruns Have to Be Financed Too
If a sewer line needs rerouting or a change order adds scope, the extra cost lands on the same deferred structure. Build a cushion into the plan from the start; our article on how much contingency to budget explains how to size one.
Putting the Levers Together Without Overreaching
Most homeowners combine two or three levers. A common pattern is staged billing paid from a HELOC during the build, a smaller promotional balance for finishes that will be repaid quickly, and rent that starts covering payments once the unit is leased.
The test for any combination is simple: list each payment, when it starts, when it can change, and what happens if the ADU is finished or rented later than planned. If you can carry every payment from your own income for a few extra months, the plan has room. If the plan only works when everything happens on schedule, slow down and adjust it before you sign. To see which offers are available for your project today, review current financing terms and bring your plan to the first consultation.
FAQ
Does spreading out ADU payments raise the total cost of the project?
Usually, yes. The construction cost stays the same, but every month you borrow instead of paying cash adds interest, and promotional balances that are not repaid in time move to a higher standard rate.
Is there a way to build an ADU with nothing paid up front?
Rarely in the strict sense. A builder needs a deposit at signing to start design and order materials, though that deposit can itself be covered by a loan or credit line, which shifts the cost rather than removing it.
Can I use D.E.P.P. to build an ADU before selling my house?
The program as published covers pre-sale renovations paid at closing and does not describe ADU construction. If you plan to sell, ask United Signature whether your specific project qualifies before you count on it.
When do the payments usually begin on a deferred ADU plan?
It depends on the lever. Interest on a HELOC or construction loan starts with the first draw, promotional financing has a scheduled start for regular payments, and staged billing follows the progress of the work.
What if the ADU takes longer to rent than I expected?
You keep paying the loans from your own income until a tenant moves in. That is why a cushion of several months of payments is worth setting aside before you rely on rent to carry the financing.