Towing Issues: breaking system required in tod car, motorhomes, pitch

Question
i am told that it is the law that you must have a extra breaking system for the
car that you are towing behind your motor home.
some say its a sale pitch --is it or is there a ruling on that  

Answer
well I know that trailer braking requirements depend on the weight of the vehicle being towed....

I have not heard of any requirement for vehicles behind motorhomes... I know there are several devices available to do this, and it is up to the person doing the towing if they want one... If you were to travel a lot of hills I might consider it..

Sorry but this is really one question I am not sure of the answers for ...