I do recommend bloodwork if it's in your budget. That way you can be sure that the horse doesn't come to you drugged. X-rays I would say yes to if the horse was doing high-impact sports, like racing or higher-level jumping or dressage, where there is a lot of strain on the joints. Unless the horse is an OTTB, or started really young, I wouldn't really worry. Flexion tests and hoof tests will generally tell you if there are any major problems. The only other thing I would suggest for X-rays is if there's any sign of navicular or any hint of laminitis, because those can go bad fast as well, given the right circumstances.
Alrightey I've rambled enough... hope everything goes well for ya!