Look first at proven experience, not the size of the portfolio. Ask for a couple of engagements that match your technology stack, and then find out whether those engineers are still with the company. A serious vendor is happy to connect you with the people who would work laravel or ruby on rails your project. Vague answers at this stage generally mean the delivery team is not the team you were shown.
The contract deserves more attention than the sales deck. Three clauses do most of the work: assignment of intellectual property, the NDA, and exit terms and handover. Everything produced must transfer to you once invoices are settled, together with documentation, pipelines and deployment scripts. Watch for any clause that leaves reusable components with the vendor, because that is often the part you cannot replace later.
Find out how the estimate was built. A credible estimate is accompanied by the assumptions behind it, a task-level breakdown and an explicit range. A fixed price is only reasonable when the requirements are stable and documented; when the scope is still moving the vendor pads the number and react native programmers for hire you pay for it anyway. Time and difference between php and python materials shifts that risk to you, so it demands a sprint cadence, demos and a budget cap.
Process beats headcount. Find out how a new requirement enters the plan, who signs off on a feature difference between livewire and react how quality assurance works. A mature team should be able to show you running software rather than status reports. Acceptance criteria in writing stay the practical protection against an argument at delivery time.
Last, consider the day you no longer need this vendor while the relationship is still good. Ask that the source repository stays under your account from the first commit, and that documentation is updated as part of the work. A vendor with nothing to hide accepts it without argument; hesitation here tells you quite a lot.
