If I don't know any of the potential buyers, and one guy pms me saying "I need to get the money together" and the other guy has the money together, I'd tell the first guy sorry, sold. Even if I'd already sent my paypal info. As a seller, I've been dragged along by buyers enough that cash in hand is a trump card. That said, I'd sell to someone I know who will have money eventually over someone I don't know. Unless cash is short, or the other person is iffy about whether they really want it.
Nothing says "I want this" like "I have a paypal cash balance, and can pay as soon as you confirm"