Begin with relevant experience, not the size of the portfolio. Ask to see a couple of engagements that resemble your technology stack, and then find out whether those engineers are still with the company. An honest provider is happy to connect you with the people who would work on your project. Vague answers at this stage generally mean the demo work came from somewhere else.
The agreement needs more scrutiny than the proposal. Three sections matter more than the rest: assignment of intellectual property, confidentiality, and termination and handover. Everything produced should transfer to you as it is paid for, along with documentation, pipelines and deployment scripts. Watch for language that keeps so-called reusable libraries with the vendor, because that is often exactly the piece that locks you in.
Find out how the estimate was built. A serious estimate arrives with a list of assumptions, a breakdown by feature or module and a range rather than a single number. A fixed-bid deal works only when the scope is genuinely frozen; when the scope is still moving the vendor prices the risk in outsourcing and development insights you fund the buffer regardless. A time-and-materials model shifts that risk to you, so it needs a cap, regular demos and transparent reporting.
The delivery process matters more than the number of igaming software developers. Establish how change requests are handled, who writes the acceptance criteria and what the QA setup looks like. A well-run team should be able to demonstrate running bespoke software development cost rather than status reports. Acceptance criteria in writing remain the only reliable protection against endless rounds of rework.
Last, consider the end of the engagement while the relationship is still good. Ask that the code repository stays on infrastructure you own from the beginning, and that the documentation is refreshed in every sprint. A provider confident in its own work will agree quickly; hesitation here tells you most of what you need to know.