Seattle DADU Feasibility
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DADU Rental Income & ROI Projection

The 15-year cash flow of a Seattle DADU on your address.

Gross rent is the easy number; net is rent minus vacancy, management, maintenance, insurance, RRIO, the property tax on the added value, the King County capacity charge and your financing. This projection runs all of it against your address — build cost, up-front fees, and a year-by-year cash-flow table with break-even and yield.

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What does a DADU pencil out at?

The same engine that builds the report, on a typical parcel: rent, less vacancy and lease-up, less operating expenses, less debt service, equals net — and it adds up on screen. All ◇ estimates.

Citywide is the cross-source median of five published Seattle asking-rent series; each band is that figure times a neighborhood multiplier.

Bedrooms
Financing

2 bed: 750–1,000 sq ft

Pay cash—

Monthly · year-1 average

Rent
—◇/mo
Vacancy
minus —◇/mo
Lease-up
minus —◇/mo
minus —◇/mo
Net cash flow
—◇/mo
Stabilised month year 2, no lease-up
—◇/mo

Investment · 15 years

After 15 years · cash position—◇Rent collected less everything paid out, including the cash you put in up front.
After 15 years · wealth position—◇That cash position plus the part of the building you own, at what it cost to build. No appreciation.

Same fifteen years, both halves: a DADU does not hand the cash back inside them — it turns cash into a building and a rent stream. Payback on the cash alone: —. Every line below adds up to these two.

—◇
Cash-on-cash · year 1 incl. lease-up
—◇/yr
Cash-on-cash · stabilised
—◇/yr
Payback
—◇
15-year cash position
—◇
Owned value at year 15 build at cost, no appreciation
—◇
15-year wealth cash + owned value
—◇
Appreciation scenario shown separately, not added
—◇

◇ every figure is an estimate

How this is calculated
  • The engine’s own sentences appear here once the estimate loads.

Every figure is an estimate (◇) from our own engine — the same rent table, cost band and fee model the paid reports use. Rent: our dated area table. See the rental ROI report and the report disclaimer.

Get your 15-year projection for your address

Inside this dossier

A 20-page sample, chapter by chapter.

The chapter index of your report — the real table of contents from the sample, rebuilt for your address at purchase.

  1. Cover1
  2. Report disclaimer2
  3. Your property from above5
  4. Executive summary6
  5. Unit assumption6
  6. Rent evidence7
  7. Cost basis8
  8. Fee, tax & charge stack9
  9. 15-year cash-flow projection9
  10. Payback10
  11. Sensitivity11
  12. Site risks to the projection12
  13. What would change this verdict13
  14. Worked examples from real Seattle lots14
  15. What to do next14
  16. Sources15
  17. Before you rely on this3
  18. Next step: the full study20

Sample pages

How it reads, page by page.

15-year cash flow — three pages from the sample PDF, generated from a real Seattle address. Your copy is built from your own parcel.

Download the full sample PDF

Method & sources

Methodology: where every figure comes from.

Every figure follows the same methodology — live public records or a dated constant, marked ★ official or ◇ estimate.

  • Seattle neighborhood rent bands + a dated cross-source median of five published asking-rent seriesstudio/1/2/3-bed rent by neighborhood band (a bedroom-count table, not per sq ft); the calculator above prints the series and the fetch date
  • City fee envelopepermit, trades, capacity charge, utility connection, studies
  • King County capacity charge + SPU drainage tiersrecurring 15-year and annual charges
  • 15-year cash-flow modelrent growth, vacancy and lease-up, management, maintenance, insurance, RRIO, property tax on added value, capacity charge

Worked examples

Real Seattle lots, run through this report.

Three Seattle addresses measured with the same engine, so you can see how the analysis lands on lots like yours.

Licton Springs — Rents about $2,800 a month
Aerial with the report's measured overlays drawn to scale.

Worked example 1 · Licton Springs

Rents about $2,800 a month

Fit check
Fit unconfirmed — a unit is already under construction on the lot, so the measured clear zone (746 sq ft) may be occupied
Projected rent
$2,800 / mo
Build cost (all-in, typical)
$518,500 (best $420,000 – recent $616,000)
Payback year
beyond 15 years (≈ year 29 on the same assumptions)
Cash-on-cash (year 1)
-16.7%

A 2 bed / 1 bath, ~1,000 sq ft DADU on this Licton Springs lot projects to rent for about $2,800 a month and cost roughly $518,500 (best $420,000 – recent $616,000) to build, financed with a HELOC. The detached unit fits the measured clear zone, so new construction is the realistic path. Even so, payback is beyond 15 years (≈ year 29 on the same assumptions) and -16.7% — the debt service dominates the early years. The projection is a planning scenario, not a promise; pull the financing lever first, because cash versus HELOC moves the return more than rent. Re-run it free with your real rate.

Beacon Hill — Rents about $2,450 a month
Aerial with the report's measured overlays drawn to scale.

Worked example 2 · Beacon Hill

Rents about $2,450 a month

Fit check
New detached unit fits the measured clear zone (1,000 sq ft footprint)
Projected rent
$2,450 / mo
Build cost (all-in, typical)
$518,500 (best $420,000 – recent $616,000)
Payback year
beyond 30 years
Cash-on-cash (year 1)
-19.1%

A 2 bed / 1 bath, ~1,000 sq ft DADU on this Beacon Hill lot projects to rent for about $2,450 a month and cost roughly $518,500 (best $420,000 – recent $616,000) to build, financed with a HELOC. The detached unit fits the measured clear zone, so new construction is the realistic path. Even so, payback is beyond 30 years and -19.1% — the debt service dominates the early years. The projection is a planning scenario, not a promise; pull the financing lever first, because cash versus HELOC moves the return more than rent. Re-run it free with your real rate.

Ballard — No detached fit — conversion path
Aerial with the report's measured overlays drawn to scale.

Worked example 3 · Ballard

No detached fit — conversion path

Fit check
A new detached DADU does NOT fit the measured clear zone — see the verdict
Projected rent
$2,800 / mo
Build cost (all-in, typical)
$518,500 (best $420,000 – recent $616,000)
Payback year
beyond 15 years (≈ year 29 on the same assumptions)
Cash-on-cash (year 1)
-15.9%

On this Ballard lot the site analysis measured a clear zone below a usable detached footprint, so a new detached DADU does not fit — the projection is a planning scenario for an attached ADU or a conversion. A 2 bed / 1 bath, ~1,000 sq ft unit projects to rent for about $2,800 a month and cost roughly $518,500 (best $420,000 – recent $616,000) to build, lower because a conversion or attached unit is the assumed path. Payback is beyond 15 years (≈ year 29 on the same assumptions), and year-one cash flow is negative under financing. Order the full feasibility report before spending on design.

Questions, answered

Before you order.

Is this investment advice?

No. It is a financial projection built from public data and dated estimates, not a recommendation. Actual rent, appreciation, and expenses will differ — a DADU's rent depends on condition, market, and management.

What rent does it assume?

The cross-source MEDIAN of five published Seattle asking-rent series for your bedroom count, times a neighborhood-band multiplier, rounded to the nearest $25. The band around it runs from 90% of that figure up to the cross-source mean. Rent is a bedroom-count table — the published series carry no size dimension — so unit size drives cost, not rent. You can choose a studio, 1, 2, or 3 bedrooms in the form; the calculator on this page prints the exact figure, its arithmetic and every source with its fetch date.

Cash or HELOC — why does it matter?

Financing changes the cash flow entirely. Cash has no debt service; a HELOC adds interest and amortization. The projection runs your choice and shows the payback year under each.

Read first — free

The free Seattle guides behind this report.

Everything this report measures is explained for free first. Read the guide, decide whether you still want it measured for your own address.

All Seattle DADU & property guides

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