EDIT: The better idea is to get the person to photo the OCCC plate & GVWR (weights) on the RV you are interested in and email or text to you. The point here is that you can have two nearly identical RVs but different OCCCs. Note the words: 'nearly identical'. Little things like a painted exterior, slightly different generator, different drive train details, interior trim and decorations, accessories, different stabilizer system will lead to different OCCCs. So you really need to know the OCCC on the coach you are looking at....
Not really! Take the GVWR of the chassis & subtract the OCCC to get the 'curb' weight. Curb Wt is weight with full fuel, lubes, full LP, ready to roll. No water or wastes.
GVWR - OCCC = Curb Weight
You can get GVWR from the internet adverts for the coach. Someone may look their OCCC up and post it. However, the OCCC is a variable #. OCCC depends on what has been added to the coach above the curb weight. Ex., If they put on a 40# sat dish and 40#s of water softener equipment, and another 20#s of other goodies, that would be added to the curb weight or, the reverse, subtracted from the OCCC.
GVWR - (Curb weight + anything added or attached to the vehicle) = OCCCnew
You must subtract the weight of occupants and fresh water in tank from the OCCC to get the payload. Waste waters doesn't count for some reason, only fresh water @ 8.34lbs/Gal. A person is 154lbs. LP is not taken out of the OCCC; it's added in the curb weight calculation.
The old, superseded, regulation using 'sleeping positions' to calculate passenger weight is no longer effective. It's passenger seating (safety belted) capacity x 154lbs.
Confusing.... They could have done better writing the regs....