A number produced without questions is a warning, not a service level. Any serious team responds with clarifying questions before any number: about users and volumes. A vendor that prices with no clarification is pricing a guess, dedicated developers vs freelancers comparison and rust web development a guess will be corrected later — on your budget.
Watch for any distance between the team in the pitch and the people who will code. Request specific people rather than roles in the statement of work, with a clause covering replacement. A team that only offers a pool of resources and will not commit to individuals is preserving the option to staff you with whoever is free.
Insist on access to the repository from the start. A team that shows nothing between demos expects you to take delivery on faith. Regular commits and pull requests tell you the actual pace far better than a slide deck. This extends to the automated test suite: if it does not exist, quality claims remain unverifiable.
Ambiguous phrasing around code ownership is never an accident. The contract must state explicitly that all outputs produced under it become the property of your vuejs company on payment. Also check the jurisdiction and the milestone terms: a large upfront payment with no deliverable attached eliminates the only leverage you have.
Finally, look at communication. Ask what overlap the teams will share with your working day, who handles your questions and within what time. A few hours of overlap generally works; zero overlap stretches every clarification into a lost day. Careless writing in the early emails will not improve later.