Before you tow, you need to know!
Flat towing a car by Tow bar or A-Frame on all four tires behind their RV is a very popular way to travel. RVing, in general, is a big responsibility and staying educated is key. When flat towing there are two things to consider. The first is towing laws for each state and country and if a braking system is required, the other is the Gross Combination Weight Rating (GCWR) for your motorhome.
In most states, you need to have a brake system if the Towed Vehicle Weight is above 3000 lbs (some states 1500 lbs). See link above.