Question: what to ask when buying a used iphone?
Answer: Inspect the iPhone's cosmetic condition. First of all, if the iPhone has a case, remove it and check the iPhone's cosmetic condition. ... 
Button test. ... 
Insert your SIM to check your network. ... 
Phone test. ... 
Headphone jack test. ... 
Check iTunes and a battery charge. ... 
Wifi test. ... 
GPS test.