I think it depends on how much money you are willing to pay. When I went shopping for my high performance jumper, I had the flexion and soundness test done, then anything that looked off I had x-rayed. Keep in mind, nothing is going to be completely perfect, but if you can afford it, I would x-ray the hocks and the front feet, which from my experience, have been the 2 areas that usually show the most changes with jumpers. Now, if you are buying a GP jumper or vetting an expensive imported horse, I would have everything x-rayed and blood work done. Also, something a lot of people neglect to check for is soundness of wind, which can impact a jumper's performance. That's pretty much all I can think of, and get YOUR vet to do the pre-purchase instead of theirs!