Start with relevant experience, not the length of the client list. Ask seo agency for software companies three or four projects that sit close to your technology stack, and then ask specifically whether those engineers are still with the government software development company. An honest provider is happy to connect you with the engineers. Vague answers at this stage almost always mean you are talking to a reseller.
The agreement needs a slower read than the pitch. A few clauses carry most of the weight: intellectual property assignment, non-disclosure, and notice periods and handover. Every artifact should transfer to you once invoices are settled, including documentation, pipelines and deployment scripts. Look closely at wording that leaves framework code in the vendor’s hands, as this is frequently the part you cannot replace later.
Ask how they estimate. A serious estimate comes with a written set of assumptions, a task-level breakdown and a range rather than a single number. A fixed price is only reasonable when the scope is genuinely frozen; otherwise the vendor pads the number and you pay for it anyway. Time and materials puts the risk on your side, so it requires a cap, regular demos and software development for fintech transparent reporting.
How the work is run matters as much as team size. Ask how change requests are handled, who writes the acceptance criteria and web app development services what the QA setup looks like. A team can show you a live build at the end of each sprint. Acceptance criteria in writing stay the only reliable protection against an argument at delivery time.
Last, plan for the end of the engagement while the relationship is still good. Require that the source repository sits under your account from the beginning, and that the documentation is refreshed in every sprint. A partner who is comfortable with this says yes immediately; a long negotiation over it tells you quite a lot.