Private individuals hauling freight for payment across state lines without a DOT number, put themselves at risk of a large fine if stopped. Trailers hauling cars are especially prone to be stopped. Generally you have to prove the car is yours and it's for your own personal purposes that you are hauling it.
See this blog entry for an example:
hauling my own stuff for my own business across state lines ? | TruckersReport.com Trucking Forum | #1 CDL Truck Driver Message Board
Not to mention there is no way anyone with experience would roll that on a trailer, strap it and take off for hundreds of miles. The subframe would need to be on rigid blocking and strapped 4 ways to be secure.
I've got a Ram 2500 diesel and 10k, 20ft car trailer and would love to make $750 but the risks stated above and liability to the owner which cannot be covered without a DOT number would preclude me from even thinking about it!
