MacBook pro
What to check when buying a used MacBook pro from someone
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Check and be sure the owner has correctly re-set mac so their personal/account info has been removed.
Later on startup, if done correctly, this should allow you to set-up the mac as though it were new. It will
not start in a full system then, without setting it up from scratch. And Nothing from former owner, etc.
If they've followed instructions here, with one noted exception, the setup will result in unused new OS.
• What to do before you sell, give away, or trade-in your Mac - Apple Support
https://support.apple.com/en-us/HT201065
Note #6:
Erase your hard drive and reinstall macOS:
"The best way to restore your Mac to factory settings is to erase your hard
drive and reinstall macOS. After macOS installation is complete, the Mac
restarts to a Welcome screen and asks you to choose a country or region.
"If you want to leave the Mac in an out-of-box state, don't continue with
setup of your system. Instead, press Command-Q to shut down the Mac.
When the new owner turns on the Mac, setup assistant will guide them
through the setup process." (this then retains an 'original first-run' status)