Billionaire entrepreneur and inventor Elon Musk has paid $17 million for a mansion in Bel Air, Calif. Built in 1990 and remodeled with entertaining in mind, the 20,248-square-foot manse features a two-story library, a theater, a library/study, a wine cellar, a gym, seven bedrooms and 10 bathrooms. The Los Angeles Times reports the 1.7-acre property includes a tennis court, a swimming pool and an expansive motor court. Musk, 41, founded Hawthorne rocket maker Space Exploration Technologies Corp., known as SpaceX. He co-founded electric-car company Telsa Motors Inc. and the Internet payment company that would become PayPal. The property previously changed hands in 1997 for $5.35 million, public records show.