A quote that comes back within a day should be treated as a red flag rather than good service. A competent team responds with a list of questions: about users and volumes. A supplier that commits to a figure before understanding the scope is guessing, and that guess resurfaces as a change order — on your budget.
Look out for any distance between the engineers on the sales call and the people who will code. Request named engineers in the contract, with wording about substitutions. A vendor that only offers abstract roles and refuses to name specific engineers is preserving the option to staff you with whoever is free.
Require access to the repository from day one. A provider that delivers nothing between demos is asking you to take delivery on faith. Regular commits and pull requests tell you the actual pace far better than any status report. The same applies to the build and deployment setup: if there is no pipeline, assurances about quality are nothing more than words.
Vague wording in the contract around IP is not a formality. The agreement should state explicitly that all deliverables become the property of your igaming software development company on payment. Check also which country's law applies and outsource mobile app development how payments are structured: heavy prepayment with nothing due in return for livewire vs vue weeks takes away any leverage you would otherwise keep.
Finally, pay attention to the working rhythm. Confirm how many hours the teams will share with your timezone, which named person answers day-to-day questions and on what response times. A few hours of overlap is usually enough; no overlap converts a five-minute question into a lost day. Sloppy written English in the early emails does not improve later.