No one can tell what will happen over the next jump or around the next barrel. Furthermore, the results of prepurchase exams often fall into gray areas. Determining the importance of the results requires skill and experience. I'll buy him if he passes the vet. This is inaccurate.
Veterinarians provide information.
The decision to buy is between the buyer and the seller. Whatever the veterinarian says, the final decision is yours. Be present if at all possible. The veterinarian will want to go over his findings with you, and developments during the prepurchase might change the procedures you want performed. Alternatively, many veterinarians require that the horse be brought into their clinic for prepurchase exams.