GVWR does not include any weight for a trailer or toad.
After extensive research and responses from numerous State agencies, I never found any State that requires aux brakes on a toad, which is not a trailer. It is known as a "vehicle in tow" and in some States you are required to stop within a certain distance and if your coach brakes can do that, you are good to go. IN other States, like Florida, and most others, you are perfectly legal to tow a toad 4 down without any auxiliary brakes. Of course you can either believe the State officials or you can believe the drivel put out by the people that sell Aux brakes. I always used an aux brake but I knew that if that system failed, I was still legal to travel without an aux brake. Here is one response, other states were similar:
A vehicle towed behind a motor home would be exempt from the braking requirements in Florida statute 316.261 as a drive away, tow away operation. Please contact me if you have any other questions.
Lt. Jeff Frost
Florida Highway Patrol
Public Affairs Officer
Commercial Vehicle Enforcement
2900 Apalachee Parkway, MS 45
850-617-2279
Tallahassee, Florida 32399