Begin with domain experience, not the size of the portfolio. Request three or hire crm developers four engagements that resemble your technology stack, and then ask specifically which engineers actually built it. A solid partner will introduce you to the tech lead. Vague answers at this stage generally mean the demo work came from somewhere else.
The contract needs more scrutiny than the proposal. Three clauses do most of the work: assignment of intellectual property, the NDA, and notice periods and handover. Everything produced must transfer to you once invoices are settled, along with documentation, pipelines and deployment scripts. Look closely at wording that keeps so-called reusable libraries outside the transfer, as that is often the part you cannot replace later.
Find out how the estimate was built. A serious estimate comes with a list of assumptions, a breakdown per feature difference between laravel and symfony a best case and a worst case. A fixed price only makes sense when the requirements are stable and vue.js development company documented; when the scope is still moving the supplier prices the risk in and you pay for uncertainty either way. Hourly billing shifts that risk to you, so it requires a sprint cadence, demos and a budget cap.
Process beats the number of developers. Ask how change requests are handled, who writes the acceptance criteria and how quality assurance works. A mature team should be able to show you running software development for fintech rather than status reports. Clear, written acceptance criteria remain your only real protection against endless rounds of rework.
Before signing, plan for the end of the engagement before it becomes urgent. Require that the code repository lives on infrastructure you own from the first commit, and that documentation is updated as part of the work. A vendor with nothing to hide will agree quickly; resistance at this point says quite a lot.