Quick answer: a focused SaaS MVP for a UK founder typically costs £15,000–£40,000 and takes 8–14 weeks to build, covering core functionality, multi-tenant architecture, and basic billing — a mid-size platform with deeper integrations runs £40,000–£100,000+. The architecture decisions that matter most (multi-tenancy, billing, and what to build vs. buy) matter more to long-term cost than almost any individual feature choice.
Multi-Tenant Architecture: The Decision That Compounds
A SaaS platform serving multiple customers from one codebase needs a clear multi-tenancy strategy decided early — shared database with tenant isolation via row-level security is the right default for most early-stage SaaS products, since it's simpler to operate than schema-per-tenant or database-per-tenant while still providing real data isolation. Retrofitting proper tenant isolation after launch, once customer data is already commingled in a shared schema without it, is a significantly harder migration than designing for it from day one — we cover this in more depth in our multi-tenant SaaS architecture writeup.
Billing: Build vs Buy
Billing logic — subscription tiers, usage-based metering, proration on upgrades, dunning on failed payments — is rarely worth building in-house. An established platform like Stripe Billing has already solved the edge cases a homegrown billing system will discover the hard way, in production, with real customers' payments on the line.
What an MVP Should Actually Include
The minimum feature set that lets real customers use the product and pay for it — not the full product vision. A SaaS MVP that tries to ship every planned feature before the first paying customer delays the only feedback that actually matters: whether real customers will pay for what you've built. Core functionality, basic multi-tenant isolation, and simple billing integration is the right scope for version one; the rest should wait for validated demand.
Realistic Cost and Timeline
| Project type | Typical cost | Typical timeline |
|---|---|---|
| Focused MVP (core features, basic billing) | £15,000–£40,000 | 8–14 weeks |
| Mid-size platform with integrations | £40,000–£100,000 | 4–7 months |
| Enterprise-grade platform | £100,000+ | 7+ months |
These ranges hold for a well-vetted development partner; a London agency typically runs 2–3x above this for comparable senior-level output, consistent with the pattern we've documented for UK custom software costs generally.
Scaling Beyond the MVP
Scale infrastructure investment to actual usage growth, not projected growth — premature infrastructure investment for a scale the product hasn't reached yet is as common and as costly a mistake as under-building for genuine growth. Add integrations, deeper customisation, and enterprise features once paying customers are actually asking for them, not speculatively in version one.
If you're a UK founder scoping a SaaS platform build and want a realistic cost and timeline picture against your actual feature list, reach out at info@digit.com.pk.