Double check that the owner properly disconnected the device from their Google account/Samsung account (activation lock/factory reset protection). Many phones will be locked to the first Google account they get signed into as theft protection. If you buy an activation locked phone, it’s possible the owner simply forgot, but it’s also possible that you’ve bought a stolen phone and will never be able to do much with it.
How hard it is to recover a locked phone depends: on some phones the owner can remotely disconnect the phone from their accounts, on others they need to enter the password and 2fa key into the phone to log in and then disconnect after. To prevent this, disconnect all Google accounts before factory resetting and make sure any manufacturer-specific lock settings are disabled. If you’re buying the phone in person, try to log into your Google account on the spot so they can’t just take your money for a useless brick.
Check the software support lifecycle. Some second hand phones will get you another three or four years of updates, some are already two years behind when you buy them despite the hardware functioning just fine. With custom ROMs you can still use them without risk of getting hacked most of the time, but if you’re looking for a new phone you may want to search for one that the manufacturer still supports.
Also get a replacement battery just in case. Make sure to factory reset the phone (from recovery, if possible) so no weird malware gets left behind by the original owner.
Double check that the owner properly disconnected the device from their Google account/Samsung account (activation lock/factory reset protection). Many phones will be locked to the first Google account they get signed into as theft protection. If you buy an activation locked phone, it’s possible the owner simply forgot, but it’s also possible that you’ve bought a stolen phone and will never be able to do much with it.
How hard it is to recover a locked phone depends: on some phones the owner can remotely disconnect the phone from their accounts, on others they need to enter the password and 2fa key into the phone to log in and then disconnect after. To prevent this, disconnect all Google accounts before factory resetting and make sure any manufacturer-specific lock settings are disabled. If you’re buying the phone in person, try to log into your Google account on the spot so they can’t just take your money for a useless brick.
Check the software support lifecycle. Some second hand phones will get you another three or four years of updates, some are already two years behind when you buy them despite the hardware functioning just fine. With custom ROMs you can still use them without risk of getting hacked most of the time, but if you’re looking for a new phone you may want to search for one that the manufacturer still supports.
Also get a replacement battery just in case. Make sure to factory reset the phone (from recovery, if possible) so no weird malware gets left behind by the original owner.