A quote that comes back within a day should be treated as a red flag rather than good service. An experienced provider returns questions first: about integrations. A supplier that prices before understanding the scope is probably guessing, and a guess resurfaces as a change order — and you will pay for it.
Be wary of a mismatch between the people you meet and the people who will code. Insist on named engineers in the contract, with a provision that requires notice before anyone is swapped. A team that only offers a pool of resources and difference between laravel and symfony refuses to name people is preserving the right to assign anyone it likes.
Require commit-level visibility from day one. A team that shows a build only at the end of each phase is inviting you to take delivery on faith. Daily commits reveal who is really on the project far better than any status report. The same applies to the CI pipeline: custom .net development if there is no pipeline, promises about quality remain just talk.
Vague phrasing around code ownership is rarely a formality. The document should state in plain terms that the code, designs and documentation transfer to your business on payment. Check also the jurisdiction and the payment schedule: a request for rust development services most of the money up front with no deliverable attached eliminates the only leverage you have.
Lastly, look at communication. Establish what overlap the teams will share with your timezone, who handles day-to-day questions and hire node js experts on what response times. Some genuine overlap is usually enough; no overlap stretches a five-minute question into a lost day. Unclear written communication in the sales phase will not improve later.