As for it being a scam, only the most ignorant person would pay $20,000 up front, via check or what ever. $20,000 would be paid in person only. If your spending $20,000, you'd fly to inspect everything before handing your cash over. Or at least pay someone in the area who knows what thier doing, to inspect it for you, and move it to a safe location.
I dont think its a scam at all. Like someone else said, it's most likely an auction house that came in and won the bid on the whole estate. Or it could be some rich ars person who just got tired of it and would rather just get something back out of it ( and someone else move it ). I can see water on the surface, in a couple pics. As for someone padding the price, this could be. Or it could be someone who has been shopping for a huge tank, thier bud tell's them about this on ebay, and had to register to make a bid. Could very well be someone knowing they could make a huge buck reselling it. Either way, he stated $20,000 was the required amount to buy, but the reserve is met at $15,000. So if he was bidding himself up, he just paid ebay some decent bucks if noone out bids him.