A number produced without questions should be treated as a warning, not a service level. A competent team will come back with a list of questions: about integrations. A supplier that commits to a figure before understanding the scope is simply pricing a guess, backend and frontend technologies we use that guess becomes a change request later — at your expense.
Be wary of any distance between the engineers on the sales call and the people who will code. Insist on specific people rather than roles in the agreement, with a provision that requires notice before anyone is swapped. A provider that talks only about a pool of resources and will not commit to people is preserving the option to staff you with whoever is free.
Insist on the source repository from the start. A provider that shows code only at milestones is asking you to take delivery on faith. Visible commits show you who is really on the project far better than a slide deck. This extends to the CI pipeline: laravel or node js if there is no pipeline, assurances about quality remain unverifiable.
Ambiguous phrasing around code ownership is never a formality. The document needs to state explicitly that all deliverables transfer to your company as they are paid vue js developer for hire. Check also the jurisdiction and the milestone terms: a large upfront payment with no deliverable attached removes your only leverage.
Last, examine the working rhythm. Ask how many hours the teams will share each day, which named person answers questions and custom development insights on what response times. A few hours of overlap is normally sufficient; none at all stretches every clarification into a day of delay. Unclear written communication in the early emails will not improve under delivery pressure.