Truck Driving Requirements!?

I wan't to become a truck driver, but it seems that every company requires you to be atleast 21. I will be twenty in october, is there any companys that hire at a younger age. Also, most companys ask for it be atleast five years since you've had any alcohol related offenses like DUI's. Will any companys make an exception on this?? I would appreciate any information, Thanks alot!