Robert,
Even in baseball, the A,AA,AAA leagues are considered The PRO's. They have contracts. Some minor leaguers make a living (carreer) playing minor league baseball (their dream). The Major League is called The Big Show
(among the players).
In auto racing, if you are racing for a money prize (purse), that's Pro. If you race for a trophy (SCCA), that is usually called Club Racing. Anyone may chime in with corrections or more info.
Again, $.02
Gene B.