房 = 户 (a single-leaf door) + 方 (for the sound). 户 is half of 门 (a double door) — a picture of one door panel. A space behind a door = a room or house.
房 means a house or room: 房子 (a house, with 子), 房间 (a room — pairs with 间, next), 房东 (landlord, 'house-east/host'). Housing is a huge theme in modern Chinese life — owning a 房子 is often seen as essential before marriage, and 房价 (housing prices) is a constant topic of conversation. The character behind the door carries a lot of weight.
A space behind a door (户) — a ROOM, a HOUSE.
户 (the left of 房) is half of 门 — one door panel. Owning a 房子 (house) looms large in modern Chinese life; 房价 (housing prices) is everyone's favorite worry.