ebay and autotrader have these occasionally
I've happened upon these type of scam sites now and then, the scam seems to be to advertise unrealistically low prices and to get folks who enquire to leave a deposit over the phone, via card. The higher the deposit the better.
But, of course there is nothing to buy, the adverts and listings are copied from genuine ads but with the offer prices lowered down to ridiculous.
When I was looking for a caravan a couple of years back, there was a yard advertised near me, he had listed about 12 caravans at stupid low prices and high specs.
I took a drive over to the location, as I knew the area, but there was nothing there when I arrived, no office, no stock, just a disused yard that was once a car dealer.
Old saying but very true, "If it seems too good to be true, that's because it is"