Ask who is actually on your team
Get named people, their roles and the percentage of their week you have. A strategy lead, a product designer and engineers who talk to you directly beat a large roster you never meet.
Ask what happens after launch
Store submissions, OS upgrades, crash triage, analytics review and a roadmap cadence should all be quoted before you sign. Products that stall usually stall in month four, not month one.
Ask how change is handled
Requirements move. A good partner prices change transparently and shows you the trade-off against scope and date rather than reopening the contract every sprint.