A number produced without questions counts as a bad sign. A competent team returns clarifying questions before any number: about who owns the data and what happens on failure. A provider that commits to a figure before understanding the scope is simply pricing a guess, nextjs development services and that guess will be corrected later — on your budget.
Be wary of a mismatch between the engineers on the sales call and those who eventually appear in the repository. Request the names and CVs of the actual team in the agreement, with a provision covering replacement. A vendor vue vs livewire that only offers abstract roles and never names individuals is reserving its own flexibility at your cost.
Require the source repository from day one. A team that shows nothing between demos is asking you to trust a black box. Regular commits and pull requests tell you who is really on the project far better than a slide deck. The same holds for the CI pipeline: if it does not exist, software development consulting quality claims remain just talk.
Ambiguous wording in the contract around IP is rarely a formality. The contract must state in plain terms that all deliverables transfer to your business on payment. Check also the jurisdiction and hire expo developers the milestone terms: heavy prepayment with no deliverable attached takes away your only leverage.
Lastly, examine communication. Establish how much working-time overlap the teams will share with your working day, which named person answers questions and within what time. Four hours of overlap generally works; no overlap stretches every clarification into a day of delay. Sloppy written English in the early emails does not improve under delivery pressure.