My sister is going through the same thing (looking for first off-campus apartment, for grad school). I told her, message anyone that looks likely (more messages out there = more chances of finding a successful match!), but don't pursue anything that feels shady and you have to justify to yourself. Not worth it. There are plenty of legit, eager, cooperative people looking for tenants/roommates. They'll be forthcoming with information, want to know about you as much as you want to know about them (no one wants to live with an axe-murderer), want to get something signed/on paper as a defense if not guarantee against either of you getting burned, and understand your reticence to send significant money into a black hole (until you've built trust by doing the above things, at least).