How to pay for an ADU: HELOC, refinance, and the real timeline

Most homeowners pay for an ADU with home equity — a HELOC or a cash-out refinance — not grants. A typical project is funded through some combination of a home equity line of credit, a cash-out refinance, savings plus phased construction, and occasionally a construction loan. Which structure fits depends on your equity, your timeline, and how you want to carry the cost during the build.

The usual funding mix

• HELOC — a home equity line of credit you draw against as you go
• Cash-out refinance — replacing your mortgage with a larger one and taking the difference
• Savings + phased construction — funding the build in stages
• Construction loan — occasionally, depending on the situation

Why a HELOC is often the best fit

For a lot of ADU projects, a HELOC is the most efficient tool:

• You only pay interest on what you actually draw
• Funds can be pulled in stages as construction progresses
• Lower interest cost during the build than taking a lump sum up front
• Flexibility if the timeline shifts

Example: if you have a $300,000 line but only use $80,000 in the first few months, you're paying interest on that $80,000 — not the full amount. That draw-as-you-go structure keeps carrying costs down while the build ramps.

The real timeline — plan your financing around it

Financing decisions should match how the project actually unfolds:

• Design + permitting: 4–6 months
• Construction: 6–8 months
• Total: roughly 10–12 months from idea to keys

That timeline has financial consequences. Carrying costs need to be planned for. Your financing should match the schedule so you're not paying for money you're not using yet. And because delays happen on any real project, it pays to leave margin.

Matching the money to the project

The right answer is specific to your situation — which structure fits, how to sequence draws against the construction schedule, and whether the project still makes sense once you plug in real financing costs. That's exactly the kind of thing worth mapping out before you break ground, not after.