You do not need a CDL until the GVWR of the truck is over 26,000 pounds, then you need a medical certificate, ect. However if it is a motorhome, then the weight does not matter, if it is your personal vehicle, it is considered a motorhome, and you do not need a CDL.
Of course if you are hired, say your employer wants you to drive a 35,000 pound motorhome for use as a office, then that would require a CDL.
In California, if the trailer is over 15,000 GVWR (does not matter if it is a 3,500 pound empty three axle trailer, just the GVWR matters) you are required to have a trailer endorsement.
You do not stop at a weight station with a pickup truck. However a flatbed truck over a certain weight has to stop at weight stations, it is not a pickup anymore.
Have fun on your trip!
Fred.
