INVEST · A PRACTICAL GUIDE
A useful ADU budget shows what’s missing.
One construction number doesn't tell you what the whole project will require. Let's separate the costs, the assumptions and the cash you may need along the way.
Put the whole scope on one page.
Start with categories: design and site investigation, approvals, construction, utilities, finishes and the costs of carrying the property during the work. Some may be part of a contractor's quote; others may sit outside it. The point is to find the gaps before adding totals.
If you're purchasing the property too, keep acquisition costs on a separate line. It should be possible to see the purchase and the project independently, then understand how they fit together. A budget that mixes them can make it harder to tell where a change actually occurred.
Ask what each estimate includes.
Put quotes beside one another only after comparing their scope. Ask about allowances, exclusions, site work and what could trigger a change. A lower total is not necessarily a lower price for the same work.
For every amount, mark it quoted, estimated or not yet known. Record who supplied it and when. This simple habit keeps an early planning figure from quietly turning into a fixed expectation. Site conditions and design decisions should feed back into the worksheet as they become clearer.
Plan for timing as well as totals.
Ask when payments would be due and what milestones they relate to. Compare that schedule with when your funds would actually be available. Keep room to discuss changes and delays with the professionals involved; don't use a contingency line as a substitute for investigating known issues.
If the plan includes a later appraisal or refinance, discuss requirements with the lender before depending on the proceeds. A projected value is not cash already available. We can coordinate those conversations, but the appraiser and lender make their own assessments.
Decide what to learn before committing more money.
You don't need a finished budget to call. Bring the property address, intended use, available quotes and the amount you're comfortable putting toward the project. We'll help identify which missing answers could most affect the plan.
Sometimes the next step is a site review; sometimes it's clarifying a quote or changing the proposed scope. We want the next expense to answer a useful question. The goal is a project you understand well enough to make decisions about, not a deceptively precise number built from guesses.
A useful next step.
ADU Property Feasibility: Central Coast Planning Questions →
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Published October 18, 2026. Local resources can change; check current requirements for your property with the relevant agency or professional.