Not obvious things to check when buying a used iPhone?

I will be buying a used iPhone 11 or 12 from Swappa soon. Would love some advice on the more nitpicky things to look at before/after I pull the trigger.

I know the obvious ones like iCloud Lock, Battery Percentage, Carrier Lock, IMEI, etc. But are there any other less obvious things I should definitely look into before and also after buying something to make sure to be sure I can get a refund if I get scammed.

I order online so can’t see the phone in person before buying it.