ADU Playbook — UnlockLand
●Academy · Playbook

The ADU Playbook

An accessory dwelling unit — a backyard cottage, garage conversion, or basement suite — is the lowest-risk way to add livable density and income to a lot you already own. This playbook covers eligibility, size and setback limits, real cost, financing, and the rental math that tells you whether it pays.

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Detached backyard accessory dwelling unit
A real backyard ADU

One extra unit, one lot — livable density you can build this year.

Where the ADU goes · 50×120 ft lot 3 placement options
Street frontage · 50 ft Primary house existing · 1,650 sf A · Detached rear yard · 600 sf A B · Garage 420 sf B C · Attached 520 sf C setback Rear yard
Placement options
ADetached cottage
Up to 600 sf · rear yard$$$
Most private & flexible · highest cost
BGarage conversion
~420 sf · existing shell$
Cheapest path where parking allows
CAttached addition
~520 sf · shares wall$$
Shares structure & services · mid cost
All options must clear the dashed setback line.

Illustrative site plan — three ways to fit an ADU on the same lot, each within setbacks and size limits.

Why an ADU is the easiest first move

You keep the main house, add one unit, and create income or housing for family — all without rezoning or assembling land. It is the gentlest possible introduction to development.

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The play

Six steps from backyard to tenant

Each step ends with a clear decision, so you only spend money once you know the unit is allowed and pays.

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Know your ADU type

Each type has its own cost, timeline, and rules. The right one depends on your lot, budget, and goals.

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Avoid these

Where ADU projects get stuck

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Does it pay?

All-in cost to payback

A worked example for a detached 600 sf ADU — where the money goes, and how long the rent takes to earn it back.

ADU economics · detached 600 sf
Where the budget goes
Construction (hard cost)$132,000
Design & engineering$30,000
Permits & fees$20,000
Utility connections$25,000
Contingency (10%)$21,000
All-in cost$228,000
The return
Market rent
$2,100/mo
Net cash yield
9.2%
Cumulative rent vs. cost
All-in cost $228k Yr 0 Yr 5 Yr 9
Payback ≈ year 8 · then pure cash flow

Illustrative economics — your real numbers depend on local cost, rent, and financing.

Run this playbook in UnlockLand

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Keep going

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See if your lot qualifies for an ADU

Run your address through UnlockLand and check eligibility, size limits, and the rough numbers in minutes.

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