Do both. Just ADD if they aren't subscribed it also gets demo'd.

Its more than reasonable that a person should be paying their sub to keep a house since on multiple occasions the developers have said its an issue of cost, resources and server space. So why should someone be able to take up a limited resource on the servers when they aren't even helping to keep them up?

Between the owner not paying a sub, the house existing creating a load and the occupied lot not allowing a paying customer to get a house the whole thing seems like an unacceptable loss to me.
House isn't used for 45 days: demo'd
House owner doesn't have a subscription for 14(?) days: demo'd