I used to be a Master Mechanic for the Los Angeles Transit System. One of my jobs was terminal inspections. This included vehicle maintenance, maintenance records and driver records. As a racer for 29 years this is what I have learned. Anything that makes money has to have a commercial license plate, (Toters must be regestered as a commercial vehicle) this includes a car such as a taxi. Any one vehicle or combination of vehicles that makes money and is over 10001 lbs has to have a DOT number. Anything over 26001 lbs. has to have a CDL of some type depending on the vehicle. There are two types of DOT number classifications. One is Interstate and the other is Intrastate. The Interstate classification means that you have to have a terminal inspection every two years done by the Highway Patrol or State Troopers. This includes all inspection and maintenance records on the vehicles and documents including random urine tests and copies of their physicals for the drivers. Even if you are the only driver / owner of the vehicle. If you register as an Intrastate you still have to keep all of the records (in case of an accident) but you don't get inspected. The problem with Intrastate is your DOT is only good in the state you register it in. Here is a couple of tips that I have learned. A Ford F250 or a GM 2500 with a triple axle goose neck is under the 26001 lbs. The diesel version are capable of towing a 15000 lb trailer. The other thing is do not advertise. Do not put any stickers of products or sponsors on the sides of your vehicles. This just gives them a clue as to what is inside. (out of sight = out of mind) Without any clues they might think it is just your weekend off road toys.

Hope this helps.
Dad