Normally if a player builds a house but abandons it later the house will stay there forever and some other player will grief at it but it will never be gone, soon this buildings will flood zones near spawn becoming a bunch of ugly structures with holes(and no one wll bother removing them instead they will go a little bit further of spawn and build another home maybe repeating the cycle).

So the solution would be lets say if the home doesn't detect a player in a week dirt may fall rock develop mold, vines wood become fungi or disappears, ultimately the home is gone or some minimums remains are left of it. Decay of things