Craig M is correct about hobbyists and RVers not being classified as commercial carriers. RVers are exempt from the CLD requirements as long as the units that they are driving/towing are registered as Recreational Vehicles. However, the minute you get involved in doing anything that you are doing to earn money, your vehicle becomes a "commercial vehicle". In "interstate commerce" (traveling across state lines), you are driving a commercial vehicle (assuming your doing any kind of business activity) if the vehicle is over 10,000 lbs! You don't need a CDL until you hit 26,001 GVW but you do need a DOT number and have to have the name of your business or your name on your vehicle.

Here in Minnesota, I know of State Troopers who have stopped and tagged drivers from out of state driving 1 ton duallys (over 10k gvw) hauling snowmobile trailers going to snowmobile races (for profit) because they didn't have DOT numbers or their business name on the truck. Sounds kind of petty but it happens. The rules may be different if you stay within your state boundries. Again, I'd check with your State Patrol for the most accurate info for your particular situation.