Using Basegame only, create a lot 3x2 (longer than deeper). Build only a foundation on it. Any shape is allowed, but make it big enough to build a house on. Package the lot and post it up here in the Foundations thread.
Download everyone else's floorplans and start building the houses based off the foundation. You are not allowed to add foundations or remove them. The house should have a second floor, a third is allowed. Basements can be added as well. Any EPs or SPs may be used but no CC.