RV CONUS-----
Got my Class B in Elko 6 mos ago (thank you Nv Nick for the assist at the time)......
Has a 24K lb GVWR Class A MH previously and no special lic required....Got a 40' Class well over 26K lbs and had to get the Class B to be legal.....It has air brakes and had to take both the written and practical for that also......Fairly straight forward testing with no surprises......26K lbs GVWR is the cutoff in Nevada.....Some states (Calif) have it set at anything over 40'......
Nv Nick, among others, is right on with his answers.......
