Three ways to work together

Between projects, yes: a Fixed-scope project often turns into a Monthly retainer afterwards. Mid-project, no: once underway, it runs to completion at the agreed price, with no refunds or early exits. Once it ends, you're free to switch models.

Any change outside the initially agreed scope gets its own separate written estimate. Until that new estimate is approved, I'll keep building exactly what was agreed in the original estimate.

Half upfront, when you approve the project plan, and the other half at the end, once the result has been reviewed and approved.

They roll over to the next month, they don't just disappear. But they don't stack indefinitely: they carry over for one month only, so let me know if your workload changes and it's worth adjusting the monthly hours block or switching plans.

There's no long-term minimum, you can start with a single month. The only limit is that it's billed in full-month blocks; if you need less than that, Hourly is the better fit.

I'll let you know as soon as I see the estimate won't hold, before doing any more work. You decide whether to continue, adjust the scope, or stop there. You're never billed for hours outside what was agreed.