I try to go at horse buying in a scientific way. Write a list at home of all the questions you need answered. That way you don't just see a beautiful horse and yourself flying through a field of daisys. You see an expensive investment. Heres a few that are always on my list
How does this horse get along with other horses?
What is his feed regimen?
How often are his feet done and does he require shoes?
Up-to-date on shots? Coggins? Worming?
Trail ride alone?
Stall habits? Cribbing, weaving, stall kicker?
Riding wise I always ask as many discipline related questions that I can think of. I trail ride so here are some of mine
Crosses water? Bridges?
Goes out alone?
What type of bit?
In shape or needs work?
Good luck! I love horse shopping!