You really want the bull tested for Trich. I know its the law in Texas - I don't know about elsewhere. It is a real problem in a lot of places.
Age wise, most bulls that have been used hard under range conditions are reaching the end of their average service life around that age. We get 10 years+ out of plenty of our bulls, but its not something you take for granted. I certainly wouldn't pay a lot for any bull of that age - they can "go" any time. When our mature bulls run out of gas, its usually in the form of a back or hip injury or somethig similar. Things just start to break down on big ol' stout bulls around that age.
Fertility is unlikely an issue for one that age.