I sold my Airstream twice on the Forum classifieds. The first time only took less than a week, but after we gave the buyers every chance to back out while they were here (they had a virulent case of aluminitis), they called a couple of days later and cancelled despite the fact they had signed a contract to buy. Always get a deposit (we asked for $500 on a $40K purchase). I kept the deposit since they had wasted our time and they really needed a lesson in how to run a business (they were going to use it for a new business). Put that expressly in a contact to purchase since not all states allow you to keep the deposit without a specific statement in a contract (Colorado doesn't require that, but it is safer to/ do so). After another week, the contacts slowed down and I paid $100 for a better ad. People noticed again and in a few days I had two offers. I asked for a little more than I thought I could get, got what I wanted after negotiations, and required payment by bank wire.
As soon as the wire went through (this was an out of state buyer), I overnighted the title and registration to the buyer (Fed Ex is a lot more expensive these days). Doing it that way means your risk is much lower. Bank wires are very safe and you can talk to your bank about it if you've never done it. Most do not charge for a bank wire at your end. I don't know anything much about PayPal, but it seems that may have been an honest offer that looked a little questionable, I did get some obvious scam offers and just ignored them.
The whole sale thing took about two weeks to get a signed contract, a few days to get the wire, a week or so for the buyer to arrange to have it transported to Alabama. When we got the money, we bought a much cheaper trailer and had plenty left over.
On deal with much less money involved, they can bring cash and you can sign it over right away. If you are concerned, you can get something to check if the cash is legit. If they want to give you a check, insist you go to their bank and cash it there. Don't take a certified, teller's or similar check‚ they can be faked. Make sure you explain your terms for payment before they come to see it so that you have no issues with them.
The Airstream is sold; a 2016 Nash 24M replaced it.