Very easy achievement. First, you must first purchase (or trade for) all properties in a color set. From there:
- Take your turn
- Use the D-Pad to manage properties
- Go to your completed set
- Hit the RB to purchase a house
- Achievement pops when you buy your first house.
Cheapest houses (and doesn't matter where you buy) is closest to start on the brown (Baltic and Mediterranean) and blue (Connecticut, Vermont, Oriental) properties, they are $50 each. The next row is $100, then $150, then $200 on the row of Green (Pacific, North Carolina, Pennsylvania) and Blue (Boardwalk, Park Place). The more expensive the house, the more rent you will be able to collect (for other achievements and ultimately winning).