A quote that comes back within a day should be treated as a red flag rather than good service. A competent team responds with questions first: about who owns the data and what happens on failure. A supplier that commits to a figure with no clarification is guessing, and the gap becomes a change request later — and nearshore software development you will pay for it.
Look out for a gap between the people you meet and the people who will code. Ask for named engineers in the statement of work, with wording that requires notice before anyone is swapped. A vendor that talks only about abstract roles and refuses to name specific engineers is keeping the option to staff you with whoever is free.
Require the source repository from the start. A team that shows a build only at the end of each phase expects you to take delivery on faith. Regular commits and pull requests show you who is really on the project far better than a weekly report. This extends to the automated test suite: if there is no pipeline, promises about quality are just talk.
Vague fixed price contract software development language around IP is never a formality. The document needs to state in plain terms that the code, rust development services designs and documentation become the property of your company upon settlement of the relevant invoice. Look too at the jurisdiction and the payment schedule: a large upfront payment with no deliverable attached removes the only leverage you have.
Last, examine the working rhythm. Confirm how many hours there will be with your timezone, who handles your questions and how quickly. A few hours of overlap is normally sufficient; zero overlap turns a five-minute question into a day of delay. Sloppy written English in the proposal will not improve under delivery pressure.