Class B and Class C are about the only thing you can do since you are only 19. Class C is a joke, its like a Shouffer for Hire (drive Limo's and shit)... Teh Class B is limited to # of axles and overall vehicle weight.
I'd rock the Class B in your situation, I believe you'd be able to drive dump Trucks and shit like that, basically anything without Air Brakes and I believe no tractor/trailer combos.
Over The Road makes money per mile, not hourly. You can only drive 10 hours, then pull over and rest 8. (this is more then likely just for Class A+).
Locally makes the money hourly more then likely.
Im going to start off locally in November driving Dump Trucks, there is a helluva lot of Construction here so, this could be pretty lucrative.