Michael Dell vs. Elon Musk

Dell got his start at 19 selling computers out of his University of Texas dorm room, grossing $80,000 by the end of his freshman year. Dell's MSD Capital owns the Four Seasons Maui, plus indirect stakes in Applebees, IHOP, Calvin Klein and reportedly Grand Central Station.

Musk, who says he's worried about population collapse, has nine children with three women, including triplets and two sets of twins. As a kid in South Africa, Musk taught himself to code; he sold his first game, Blastar, for about $500.