Be cautious, there are some reasons a person won't have PayPal, but I'd certainly want a positive reference from someone. If you're determined, ask for some verification, like pictures in a pattern, not random piles of something lifted off the internet. Beware of unsolicited offers, beware of certain countries more than others. You're probably going to be safer using a reputable seller, unless you're being offered something nobody else has, which is also a red flag.
It can be a risk, however certain countries and persons just don't have Paypal, you need it linked to a bank, and sometimes it's not allowed or practical. However, the only times I've paid not using a secure system, I was confident of the outcome being in my favor.