This issue comes up quite often in CA. I just retired from the California Highway Patrol after 29 years, the last 10 years as a commercial enforcement Officer. California Vehicle Code section 12804.10(a) states that a House Car (Motorhome) of 40' or less, not including the bumpers can be driven with a class C license. Over 40' requires a noncommercial class B license with a house car endorsement. No where in the law does weight come in to play with motorhomes. Towing a trailer is the same no matter what class of license you have. Under 10,000 lb GVWR trailer any license class is ok. Over 10,000 lb GVWR trailer you need a class A license.