I have had good experience with Craig list seller in highly technical city, such as San Mateo, San Jose etc.

Facebook Marketplace almost all of phone for sale is locked/stolen or the person selling does not know originator (f.e. Verizon phone never unlockable, includes all reseller) and often they are too non technical to know if it was bought from google play store ("factory unlocked") Often it will not even be paid off or intentional to scam you with a phone that will work for a month until it is reported stolen and unpaid loan