I would think if someone is not able to afford a $15 MMO subscription on a semi-regular basis they have bigger problems to think about than losing their virtual house. As it is, you can be subbed for a month and then have a six week break without losing your house (just remember to log in and visit your house on the last day of your sub). That's just $6 a month on average to keep your house.

Also I would think there are games which provide a more comprehensive interior decoration experience and aren't subscription based so you can keep your houses indefinitely.