Towing a cargo van

Just to be clear: you want to tow a loaded cargo van behind your motorhome?

Check how much the cargo van weighs, including whatever you intend to pack in it. I suspect it will be quite a bit more than your motorhome's hitch is rated for. A short wheelbase GMC Savanna 2500 apparently weighs about 5300 pounds empty, according to the GMC website. Ford E-series vans are, I believe, comparable in that regard, but it's harder to verify since the Ford website is hawking the new Transit's instead. Most class C hitches are rated at 5000 pounds or less.

Assuming your hitch is adequate, it would seem to me that you would want brakes on something that heavy regardless of specific legal requirements. The brakes on the RV have plenty to deal with just with the weight of the house; adding a few more tons that they have to stop could well make them dangerously marginal.

IMHO a much better plan is finding a friend with some free time and a sense of adventure to drive the cargo van while you drive the RV.

You need to check with the DMV folks in each state, seems that CA requires braking on anything towed that's over 1,000 lbs but that may not apply to a towed vehicle only for trailers, etc. You should be able to contact the three DMV's by getting on their websites and see what the regs are.