I'll build your web app on Next.js and Supabase (Postgres, Auth and Storage), with row-level security from the first table: sign-in, user roles, your data model, admin screens, and email and Stripe payments if you need them. It's the same stack I run my own SaaS products on.

We start by writing down who uses it and what has to work on day one. You get a fixed price and a written scope before any code, and it covers deployment and a handover. Prices start at $2,500 for a small app.