I need a 20' trailer that can double as a car hauler.

I looked a bit online, a 20' trailer with a car ramp weighs about 3500 pounds.

So my next question is how much cargo would I be able to pack inside the trailer before I exceed the GVWR of the truck? Skids, boxes, etc. I need to be able to move 2-3 tons.

I do have to have a crew cab, or at least a supercab for passengers, dog, kids, etc.