Originally Posted by A knack for horses
And on a side note, ALWAYS make the seller ride the horse first. If they aren't willing to get on the horse, just get in the car and leave. They know what you don't, so don't put your life in danger.
I totally agree, but I do have one exception.
When I was looking at my horse, the owner refused to ride him. Finally, she was backed into a corner (not literally xD) and she knew she had no choice but to get on (she only sold this horse because she needed the money). We could tell she was absolutely terrified, and she could hardly make him walk forward.
We still bought him, and he's turned out to be the best horse I've ever ridden.
But yes, it was a HUGE gamble.
Anyway, I think the best way is to ask for a vet check and/or a week trial. Whether you plan on doing it or not, you will know what's going on based on their reaction.
If it is a defiant yes, go for it.
If they refuse, assume the horse is drugged and leave.