A PPE will/should include Xrays and blood work. Quite expensive usually.. and an exam that discusses why he is stiff behind to boot. The exam may well run $300 to $500. That is a lot.. and it may get you not buying the horse. HOWEVER, if the horse is mechanically unsound for some reason, fixing or maintaining can run into thousands of dollars.
A favorite saying of mine when looking at an Ex Racehorse GELDING is you can't race the papers... you got to race the horse.
There is something about the outside of a horse that is good for the inside of a man. ~Winston Churchill
) Dinosaur Horse Trainer