May, or may not, be a scam. Reading his web site, I would guess he would best be classified as an agent. He has a computer program that "harvests" ads for motorhomes off the internet. Most are probably "by owner". He states that the MHs are housed all over the country. Interested? he will "get the deal done".
He won't give out a VIN number for the same reason many realtors don't publish addresses. Too easy for you to find the actual owner and strike your own deal. as for the $10,000 being a sign of a scam, maybe enough people go for it for him to take the reputation hit.
Then again - maybe ...??