I've done this twice, with good results both times.
The first was my 2003 Bambi. Vinnie from North Bay Airstream Repair, was selling it for a customer. He's well known and highly trustworthy, so that one was easy.
My 22' was from a private party 1000 miles away, advertised here. It was only 3 years old at the time, gently used. We talked on the phone several times, and I made an offer with the condition that everything was as described. He agreed, and I drove out. Everything was great, and we exchanged money and title at a credit union.
Check the trailer out verbally and with photos as best you can. If you think it's the one go get it.