Interview five prospective customers before writing code, asking for recent examples, not opinions. Map pains to value promises, then validate willingness to pay by proposing draft plans. Capture must‑have workflows that influence billing logic, such as seats, usage meters, thresholds, or approvals that trigger invoice line items.
Reduce scope ruthlessly while ensuring one paid path works end‑to‑end: signup, plan selection, payment, invoice, and receipt. Avoid edge cases at first, but document them. Prove one happy path across web and mobile, then expand entitlements, discounts, and proration rules once telemetry confirms stable conversion.
Order work to generate learning early: first, a concierge onboarding; second, a limited paid beta with invoices; third, self‑serve plans and trials. Celebrate each checkpoint with a retrospective. Share findings with finance and support so pricing, refunds, and invoice disputes never surprise your frontline team.