I sold a guitar on Facebook once. Was back and forth with the guy and agreed a price a fair bit lower than what I listed at. He then drove over from West Brom with £ 10 less than that agreed price, and got the arse when I wouldn’t accept this new, un-agreed price on principle. He rang his missus who supposedly transferred the extra tenner to my account (she hadn’t). Took about an hour to get him out my house, and then he was messaging and ringing for weeks after saying he would pay the extra tenner if I drove the guitar over to him.
Never again….