Pawn shops can be a good source as well. Just be ready to wipe it. The one I got had a lot of gay porn on it. Unix DD write to every sector on the drive then re partition and low level format and then reinstalled.... oh and Clorox wiped the whole thing including battery, DVD drive, screen, power cord etc.
Perhaps a tad overkill but I wanted it to be clean. No problems since.
Great advice re cleaning.
(I’ll admit that I’ve ruined many a thing because of my addiction ... to Clorox. I love the smell of it better than any smell in the world ... other than some bleach on top of bleach.)