Get a class B CDL and you should be good to go. A class A if you think you will go air brakes and heavy trailer at some point.
A class B does him no good at all. If he is a combination vehicle (towing a trailer) he has to have a Class A CDL if anything at all. Class B licenses are for straight trucks and buses.
Each state has their own requirement. Federal laws apply if you are on a federal highway or leave your home state. Farm exemptions are not very forgiving when it comes to CDLs. Might get you around a log book and things like this. Typically you have to have a log book if you drive more than 100 miles from your home terminal or cross a state line or work more than a certain number of hours. The Federal motor carrier rules change every year so you will have to check your local MVD for a CDL manual and this will give you the latest.
I was a motor carrier cop for 15 years.
