Technically, players have paid for the house and the land in full. Owners before never had to pay this extra money to maintain the houses, and banks cannot suddenly start charging you a monthly fee after the contract's been signed and the money paid.
What this is, is a government taxation law coupled with eminent domain. I know it's a technicality, but essentially it's a change in government law that is increasing taxes on the land owners. The government then pays the owner fair market value for the house (usually much lower than what you expected, what a surprise), and then takes the land from you to do with it whatever it wants (because the land you live on and paid for is still technically your government's).
Also, I don't see understand this myth about multi-home owners being cheaters. They got around the system early on it's true, and it is a little unfair for them to own two houses when so many people are without, but I wouldn't call anything they did as a cheat (unless they actually bought gil or RMT'd).
