Tiny house on a 1×1 lot under $20.000 designed for a starter family with 2 sims. Notice the efficient usage of the space under staircase. Size: 67 squares (not including 5 squares of staircase void). Designed in July 2012.
Lot size: 1×1.
Lot facing: South.
Lot price: $9.919 (with minimal and cheapest furniture) / 19.970 (having best possible furniture without exceeding $20.000, including computer and lights, as shown in photos).
Building size: 6×6 squares.
Floor area: 67 squares.
Expansions requires: none, only base game.
PS: I do not know how to create such small lots like 1×2. I downloaded them from ModTheSims.info (Mini residential lots by MaryLou).