Ask all twelve. The answers matter less than whether the supplier has clearly thought about them before.
Ownership and exit
1. Does all IP transfer to us, in writing, on creation rather than on final payment? The most important question on this list. "On final payment" leaves you owning nothing if a dispute happens mid-project.
2. Whose name are the developer accounts and repository in? Owning the code but not the App Store account still leaves you unable to ship an update.
3. If we wanted to move to another developer next month, what would we need from you? A good answer is short. A vague one is a warning.
Scope and price
4. What is the price, and what would change it? If the answer is a range, ask what would put you at each end.
5. What is explicitly out of scope? Suppliers who cannot answer this have not thought about scope, which means it will move.
6. What happens if it takes longer than you estimated? Listen for who pays. That single answer tells you how the whole relationship is structured.
Delivery
7. Who exactly will do the work? At an agency, the people in the pitch are frequently not the people who build it.
8. What do you need from us, and when? A supplier who has done this before will have a specific list. One who says "just your feedback" has not planned it.
9. What is the most likely reason this project slips? The best answer names something real, usually late feedback or content. A supplier who says nothing will go wrong has not run enough projects.
Judgement
10. What would you tell us not to build? The most revealing question here. Anyone who wants to build everything on your list is selling hours, not thinking about your problem.
11. When is your service the wrong choice? A supplier who cannot name a case where they are wrong is either inexperienced or not being straight with you.
12. Can we speak to a client in a similar situation? Not a logo wall. A conversation.
Three red flags
Common questions
What is the single most important question?
Does all intellectual property transfer to us, in writing, on creation rather than on final payment. It is the one with the largest downside if the answer is wrong and you find out late.
Should I always get three quotes?
Get three conversations. Comparing three quotes for three different interpretations of your project tells you very little; comparing how three suppliers think about your problem tells you a lot.
Is a big agency safer than a small one?
Safer against one person leaving, yes. Not safer against your project being deprioritised behind a larger client, which is the more common failure at bigger firms.