1 wc, 1 shower/tub and 1 bed are the basics. then 7 other items to get to a total of 10 so Karry didnt come to buy. no need of walls or windows, or roof...the game just ignore all of them as long as you have 1 door. in fact even if you create separate areas, the game still just count the number and type of object in the game. So if you need to create a "garage", you just need to buy the right door [even more then one if you want] and the game recognize it...same for bathrooms...if you want 3 of them, just buy 3 wc and 3 showers...it's not important where you put them. This game fool us pretending rooms and walls matter...they dont!