db, I can speak only from what I saw. The lady in the barn I used to board got a horse with sarcoid on his head. It was just a bump, but then it did grow up really fast and big and ugly looking (it was behind the ear). So vet did several removals, and then she kept putting medications on spot for very long time. So no riding, but lots of expenses.
Personally I'd probably pass on that horse or at least look around more before getting back to it.
"Life isn't about waiting for the storm to pass: it's about learning to dance in the rain..."
"When we are no longer able to change a situation - we are challenged to change ourselves."
"How people treat you is their karma; how you react is yours."