You know what? I think you're right - people mustn't be allowed to do whatever they want with their money when it comes to housing. You bought a plot? Build a house goddamit! And decorate the yard! Your empty lot hurts the feelings of the homeless.
I think we also have to go further with this and establish a special housing committee, that will go from door to door and check wherever there is a house built on the owned plot and the yard is decorated. It will also check that yard decoration is at least 80% of the limit. If not, the committee first contacts the owner and warns him about the decoration problem, if that doesn't help, the committee should have the full authority to contact SE and have the house ownership relinquished from the owner to a more responsible person.