So pretty much the only issues with ball pythons is usually caused by their keepers. Like some people already mentioned, respiratory infections, mites and an occasional bite from from a live mouse or rat is pretty much the only things you have to watch out for.
With that said, they're great beginner snakes. Some people say they're kind of boring, but if you're looking for a snake with a good temperament, that doesn't get very large and that's easy to take care of, ball pythons is the way to go.