If it sounds like the perfect horse get a vet check, see what the problem is, if its serious, or will still be ok for riding. Just becuse a horse is not 100% sound doenst mean they cant be a good horse.

I have a paint gelding who I know would not vet sound, he is toed out on one leg, and strides funny (off in the front) , does great on a joint supplement, but he is a killer cow horse for the ranch, and great at penning, and justa wonderfull broke horse.

Another rescue mare had an old wire cut on her pastern, and had partially fused joint, not sound, but it didnt cause her pain, and she was a killer kids horse.