I'm talking about 5 tons. I read the Florida DOT regs again today and see the straight truck/personal use exemption but nothing about air brakes other than an endorsement. I'm afraid if I called them and talked to 3 different people I'd get 3 different answers.
You will get 3 different answers. You should take Ruppster's advice, copy the statute that states the personal use exemption, make notes of people you talk to and keep them with you.
If you can get it tagged as a RV, all the licensing problems go away. Several years ago I read on an RV forum about people with Semi-truck tractors pulling a "RV" and getting away with a regular DL. However, if you unhook the trailer, it's no longer a RV.
The rules we all hear about weights etc. basically mean above a certain weight or number of axles a state (this varies by state) determines a vehicle is commercial and requires a CDL. That your vehicle is not commercial is what you have to argue on the side of the road. This is the same argument you have to make if your city determines no parking of commercial vehicles above a certain weight or number of axles. The weight or number of axles determines what it is.
Attached is the page from the 2009 FL CDL manual that deals with CDL requirements. The requirements vary state to state. This is for FLORIDA. You can look up the latest version.
The key here is does the single vehicle GVWR exceed 26,000 lbs. For a 5 ton the answer is yes. GVWR is what the manufacturer says, not what you tag it for. The air brake test is part of the pre-trip inspection for the CDL. Florida doesn't have a non-commercial CDL. I don't think you can get the air brake endorsement without a CDL in Florida.