Portfolio and similar projects
The first thing to ask a contractor for are examples of completed work. Ideally, they have experience in your niche: fintech, B2B SaaS, mobile apps or AI solutions. Look not just at visuals, but at architecture: how did the system scale, what were the complex solutions?
Team experience and composition
Find out who will work on your project. How many years of experience do the developers have? Is there an architecture specialist? How is their work organized? Red flag: when they won't give you contacts of the actual people who will support you.
Process and communication
Ask for a description of the process: how does discovery happen, when are demos held, who does code review? How often will you receive updates? The ideal contractor demos every two weeks and always answers questions.
Technology stack
Make sure the technologies used fit your task. Don't look for a contractor who "knows everything" — look for one who is confident with your specific stack.
Contract documentation
Read the terms carefully: how is time calculated, what happens if requirements change, who is responsible for support after launch? Red flag: vague deadlines and unclear terms.