I took my current horse on knowing he had arthritis in three legs, he was a dressage horse and his joints had just taken quite a hammering.
The owner wanted rid because he was no longer able to compete. (I found out after that she was going to have him PTS, but vet said no he's still good just not for the level of dressage she wanted.)
He wasn't on any supplements at all, and pretty basic feed.
All I wanted was a happy hacker, who I could pop over a jump every now and then.
I don't have time to do anything else.
Plus I'm a sucker for waifs and strays.
I spoke to his vet and got his complete back ground.
Had him 4 years now, his arthritis isn't a problem as its managed with an appropriate amount of work, and supplements.
I weighed up what I was prepared to risk. I didn't think his arthritis was bad, even though with his prevous owner month's before, he'd cost her a fortune in vets bills from crippling lameness in three legs.(as far as I know he been in hospital)
For me my no no's would be back problems, laminitis, sarcoids
Most other things, I'd want to know as much about as possible so lots of research. worst case scenarios, levels of management of a problem, along with the relative costs of those levels. Before I made a decision.
I put sarcoids on my no list, because yes I've seen the massive mess they can become. Rubbing on the inside of their legs, a huge pussy lump right were rug straps go. For me sarcoids are to random a thing, to manage.