Investment tools

What Might an ADU Cost and Produce?

Estimate construction cost, financing, rental income, NOI, cash flow, and return metrics under your own assumptions — then see what's actually driving the result.

What this tool does: turns your own construction, financing, and rental assumptions into project cost, NOI, cash flow, and return metrics. What it doesn’t do: provide a builder quote, an appraisal, a rent guarantee, a loan quote, tax advice, or a promise that an ADU can be built here — those all still require verification with a builder, lender, or your municipality.

Results are calculated entirely in your browser from the numbers you enter — nothing is saved unless you choose to share it below.

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Questions

Frequently asked questions

Is this an ADU construction quote?

No. The construction cost figures are wide, editable planning assumptions you control — not a bid from a builder. A builder needs to review the actual property before real costs, site work, and feasibility are known with any confidence.

Does this tool guarantee I can rent the ADU for the amount I enter?

No. Expected rent is an input you provide, based on your own knowledge of the local rental market — this tool never estimates or invents a rent figure from public data.

What's the difference between NOI and cash flow?

NOI (net operating income) is rental income minus vacancy and operating expenses — before any financing cost. Cash flow subtracts the ADU's debt service (and a CapEx reserve) from NOI. A property can have healthy NOI and still have negative cash flow if the financing cost is high relative to the income.

Should I preserve my existing mortgage or do a cash-out refinance?

This tool shows the tradeoff — how much of a full refinance's cost comes from repricing your existing balance versus financing the new ADU capital — but it doesn't tell you which is better. That depends on factors (how long you'll stay, your other cash needs, current rate spreads) this tool doesn't know about your situation.

What if the numbers show the ADU loses money?

That's a legitimate, useful result. This tool will show negative cash flow clearly if that's what your assumptions produce, rather than implying an ADU is always a good investment.

Author: Todd McClean, Realtor® | Real Estate Investment Strategist, Mountainland Realty, Inc.. Reviewed August 14, 2026. This tool provides general real estate information and is not legal, tax, accounting, lending, securities, commodities, or financial-planning advice.

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Optional next step

Want a property-specific build estimate?

Your results above are complete on their own. Planning estimates are useful for screening — a builder needs to review the property before construction cost, site work, utilities, and feasibility can be known with confidence. Todd is not a lender; use these assumptions when talking with one.