Now a judge on ABC's "Shark Tank" and owner of the Dallas Mavericks, Mark Cuban became a billionaire in 1998 when he and Todd Wagner took their online audio streaming company, Broadcast.com, public. But Cuban wasn't always a master, money-wise. In his 20s, Cuban struggled to keep himself on the right side of his credit card debt. "The hardest lesson I learned was getting my credit cards ripped up," he told Money during a recent interview. "I would charge something and think I would be able to pay it off and then not be able to. I can't tell you how many credit cards I had ripped up." Over time, Cuban learned an important lesson. Not only does credit card debt add up quickly, but borrowers end up owing vastly more than they intended to spend in interest if they don't pay it off right away.

Mark Cuban, businessman, investor, film producer, author, television personality and philanthropist. Mitchell Leff | Getty Images