Open Your House to Strangers
Villa by the sea, on a hillside in the Castellammare area of Pacfic Palisades, listed with Airbnb.
courtesy Airbnb
An extra room is great for an older parent someday—or rent-paying tourists now (if you live in a vacation spot and can list on Airbnb). "Make sure it has a separate entry and feels like its own space," says Florida architect Bud Dietrich. Figure $150 to $200 a square foot if you're remodeling or converting a basement or garage; $200 to $300 if adding on. For a 450-square-foot space, that's $90,000, leaving $10,000 to furnish it (don't skimp if you want vacationers).