Elon Musk, world's richest person with $282 billion fortune, has sold his last remaining home, a 47-acre Bay Area estate in Hillsborough, California, for $30 million, according to MLSListings.com. The property was listed for $37.5 million earlier this year. Tesla CEO Musk had said he was downsizing his life to work on sustainable energy for Earth and making life multi-planetary.