A number produced without questions counts as a bad sign. Any serious team responds with clarifying questions before any number: about integrations. A vendor that prices with no clarification is simply pricing a guess, and the gap will be corrected later — and you will pay for it.
Watch for a mismatch between the engineers on the sales call and the developers actually assigned. Ask for specific people rather than roles in the agreement, with wording covering replacement. A provider that only offers a pool of resources and refuses to name specific engineers is keeping the option to staff you with whoever is free.
Ask for commit-level visibility from the first week. A team that delivers nothing between demos is asking you to trust a black box. Visible commits reveal the actual pace far better than a slide deck. The same holds for the automated test suite: if it does not exist, assurances about quality are nothing more than words.
Vague wording in the contract around code ownership is never an oversight. The document needs to state explicitly that all outputs produced under it become the property of your fintech development company as they are paid for. Look too at the jurisdiction and the payment schedule: a large upfront payment with nothing due in return for weeks eliminates your only leverage.
Lastly, examine how they communicate. Establish how much working-time overlap you will share with your working day, php framework compare who is expected to answer questions and on what response times. Four hours of overlap generally works; zero overlap stretches every clarification into a day of delay. Careless writing in the early emails will not improve later.