Begin with relevant experience, llm integration services not the length of the client list. Request a couple of projects that match your domain and your stack, and then ask who actually wrote that code. A serious vendor is happy to connect you with the people who would work on your project. Evasive answers at this stage almost always mean the delivery team is not the team you were shown.
The contract needs a slower read than the pitch. A few clauses carry most of the weight: ownership of the code, non-disclosure, and termination and handover. Every artifact has to transfer to you as it is paid for, together with designs, scripts and infrastructure configuration. Be careful with language that keeps framework code with the vendor, because this is frequently the dependency that makes switching painful.
Ask how they estimate. A serious estimate is accompanied by a list of assumptions, a breakdown per feature and a range rather than a single number. A fixed-bid deal is only reasonable when the scope is genuinely frozen; when the scope is still moving the supplier prices the risk hire developers in usa and you pay laravel or node js for backend it anyway. Time and materials moves the risk back to the client, so it needs a sprint cadence, demos and livewire vs react comparison a budget cap.
How the work is run matters more than team size. Establish what happens when the scope changes, who signs off on a feature and how testing is organised. A mature team should be able to walk you through running software rather than status reports. Written acceptance criteria are the practical protection against the it-was-never-in-scope conversation.
Last, think about the end of the engagement before it becomes urgent. Insist that the code repository stays under your account from day one, and that a readme and architecture notes are kept current as the code changes. A provider confident in its own work will agree quickly; resistance at this point says most of what you need to know.