Look first at proven experience, not the size of the portfolio. Request a couple of engagements that match your stack, and then ask specifically who actually wrote that code. A solid partner is happy to connect you with the tech lead. Answers that name nobody at this stage usually mean you are talking to a reseller.

The contract deserves more scrutiny than the proposal. Three clauses do most of the work: assignment of intellectual property, the NDA, and exit terms and handover. Every artifact has to transfer to you once invoices are settled, along with source code, nearshore development company designs and infrastructure as code. Be careful with language that leaves framework code with the vendor, as that is often the part you cannot replace later.

Ask where their numbers come from. An honest estimate is accompanied by a list of assumptions, a breakdown by feature or module and a range rather than a single number. A fixed-price contract works only when the requirements are stable and documented; otherwise the provider prices the risk in and you pay for it anyway. Time and materials shifts that risk to you, so it requires a cap, regular demos and transparent reporting.

Process matters as much as team size. Find out how change requests are handled, who defines done and what the QA setup looks like. A mature team should be able to show you running software development technologies rather than status reports. Acceptance criteria in writing are the only reliable protection against endless rounds of rework.

Before signing, think about the end of the engagement while the relationship is still good. Insist that the code repository sits in your organisation from the first commit, and that documentation is updated as part of the work. A partner who is comfortable with this says yes immediately; a long negotiation over it reveals quite a lot.