Have bought and sold, local and long distance.
Just use common sense, if it seems to good to be true-It Is. Do request a video, or dated pictures, ask lots of questions, both good and bad. Every horse has @ least one bad habit. Request vet records. Remember you are dealing with horses they are NOT bombproof, they can be woonderful animals but they are animals with survival instincts.
Just the facts- Prospect=he doesn't know anything yet Free jumps 4 feet= Over the pasture fence Sensitive=spooky/unpredictable
This is my favorite, EVENT prospect=Crazy
Keep your eyes/ears open to interpret what is really being said, do your homework.
Go see the horse if possible, and know your REAL riding limits. If your a beginner rider that trail rides western. It would be a waste of time for both buyer/seller to look @ a Grand Prix showjumper.
It's not hard, to buy or sell. If its not something you would do face-toface, certainly don't do it on-line. And NEVER give out any personal information.