My meager research on this topic a few yrs back found that most states require a license endorsement if driving a MH over 26000 GVWR. Most states, including my own NV call it a Non commercial Class B. The Nevada test I took was extremely comprehensive and the driving portion lasted close to an hour. As to the issue of getting in an accident and not being properly insured, I agree with the poster who brought out the fact the insurance company probably could not refuse to pay a claim of an improperly licensed driver. HOWEVER, should you cause an accident that kills folks, the other parties' lawyer is going to bring it up. The punitive damages are going to hurt big time.