No, they buy the land underneath your house for $50,000. They can then charge you a use fee for the land. If you don't want to be charged a use fee, you publish a higher price for your land.
How does the use fee get set? I think you're simplifying things too much. Creating a land market where people can be forced to sell their land that they don't want to sell doesn't seem like it'd work.
I am probably missing something, but why can't they buy the land and charge you $1,000,000,000,000,000 an hour for the use, so you have to leave the house?