We have a Ball and a California King Snake (which are similar to corn snakes). The Ball is definitely more docile. Our King is very active all the time and the Ball just sits there, unless he's hungry.
Both our snakes are very tame, although neither was when we got them. If you get a baby snake, they will be jumpy and tend to bite, but like ANY animal, with handling, they will grow out of that.
We find both snakes require the same maintenance. The Ball would be more apt to sit in your lap for long periods of time as the corn snake would like to roam.
We have not had any problems with our Ball with regards to illnesses. I would do some serious searching on the web. Do lots of reading. Different people have different views and experiences. Visit lots of sites about snakes, not just one or two. Go to the library and see if they have any books on snakes. Go to the pet store and read any books they might have.
Definiately get a small snake, one that won't get any bigger than you. So, King snake, Rat snake, Corn snake, some boas, like the Ball or Sand boa are a good start.
Good Luck