After driving a F350 and hauling a welder for 40+ years in numerous states I got pulled over by KY State Police Division of Vehicle Enforcement.
I was hauling my welder set up and pulling an empty trailer as a Private Carrier.
Even though the truck is owned and licensed to me personally I must have the following.
1. A Valid Medical Card. Get a blank from the same place you get your drivers license.
2. U.S. DOT Number.
http://www.fmcsa.dot.gov/registration-licensing/online-registration/onlineregdescription.htm3. Name and DOT # on each side of the truck in 2" block letters.
4. Annual vehicle inspection.
5. License plate on vehicle to cover weight of your entire rig - trailer and all if you pull one. I Have 22K.
6. Trip Log Book for any trip I make over 100 mile one way as the crow flies.
7. Unified Carrier Registration.
http://www.ucr.in.gov/Not one question was asked about any of the gases (Acetylene, Oxygen, CO2, 75/25 Mix, gasoline or propane) that I carry in various tanks or how they were secured.
If you are 26K and over total weight or GVW the ball game completely changes.
Other than a regular doctor visit the only thing that cost was the Unified Carrier Registration $76.00
Any thing besides an RV over #10000 GVW require the items above.
Does not make any difference what your total weight is its taken from the GVW of your truck and trailer ID Tag. My Truck 10K and trailer 10K.
I received a Citation for not having a DOT or Medical Card. Court cost and all $194.00
Told that all this went into effect Jan 1 2012.