The later housing system in MO1 has been very nice. The restriction for placing a house has been enough flat space. The maximum size of a house has been 3x3 modules per level and 3 levels maximum. In total you could place 27 modules (26 in fact, because the base module had a size of 1x2 "rooms") with additional stairs inside, with windows, inner walls and inner doors, and, most important, with crafting tables and chests inside the house.