Not a thing wrong with getting a horse off the track, get a good vet check and make sure no bone chips anywhere on legs. I have had many horses off the track
Abscesses, mouth problems, leg problems, training problems, stomach problems, ect...but they are used to being stuck with a needle and sprayed with a hose.
Its really important to ask why they are retiring from racing, and then get a thorough vet check done to back up whatever story you're told. I would be prepared to spend quite a bit on the most thorough vet check you've ever done.
There are some great bargains to be had, particularly on geldings because many don't run beyond their derby year. With that being said, know who you are buying from and how they have been handled and invest in a comprehensive vet check.
Barrel prospect
