A first release you can use sooner.
We agree the smallest version that solves the core problem, then build it in milestones you review. Later ideas are planned separately, so the first release stays within its fixed price. The technology, such as Laravel, React or Next.js, is chosen for the job, and the code is yours at handover.
Two projects I have built, with what each one does: Salah Auto Hub and Islah Trust.
If you are planning a portal, read how to write a client portal brief.