Mark Cuban has always seen the Next Big Thing coming. Developing early computer networks made him a millionaire at 32. Delivering live sports over the Internet upgraded him to billionaire at 40. (To celebrate, he bought the NBA's Dallas Mavericks for $280 million.) These days he's leading the high-definition TV bandwagon. His pick for the next Next Big Thing? Himself. Starting this month, Cuban stars in The Benefactor, an ABC reality show in which 16 people compete to win $1 million in a game with no official rules. He's got more money ($1.3 billion) than God—well, Oprah anyway—so why is he doing this? Says Cuban: "It seemed like fun."

His usual idea of fun: ranting at the refs at Mavs games until he's slapped with a fine—so far he's paid more than $1 million in penalties—then matching that million with charitable donations, just to show up the league and grab a few more headlines. Love him or hate him, Cuban, 46, has made a name as a loudmouthed billionaire in T-shirts and jeans, unconventional and irrepressible. Once he blurted out that the NBA's head of officiating "couldn't manage a Dairy Queen" and drew a tongue-in-cheek challenge from the fast-food chain. He took the bait and ran a DQ for a day.

Suffice it to say The Benefactor's challenges make lemonade-selling on The Apprentice seem like a Harvard MBA seminar. The competitions are loosely based on his career—even the Jenga death match. In one test, "I told them you have to work hard but also play hard," he says. "So they had 24 hours to make as many people as possible laugh and smile."

Between such challenges, The Benefactor is peppered with "Markisms," in which he talks about his scrappy personal history. His dad, Norton, owned a car upholstery shop; his mother, Shirley, sold real estate part-time. Mark first showed his own entrepreneurial spirit at 12 selling garbage bags door-to-door in suburban Pittsburgh. (He had his own letterhead made.) He initially paid his Indiana University tuition by starting a chain letter that brought him cash-filled envelopes. "He was always a hustler," says Norton, 78. Before he could legally drink, Mark and some pals bought a bar. "God forbid it had gone really well;" he says. "I'd be in Bloomington right now, tending bar."

Instead he moved to Dallas, founded MicroSolutions and then Broadcast.com. After selling both, he now lives in a $14 million mansion with his wife, Tiffany, 32, and daughter Alexis, 1. So how did he juggle his businesses—in addition to the Mavs and the HDNet TV network, he owns the Landmark Theaters chain—and spend 12-hour days on The Benefactor? "Most people separate all parts of their lives—home, work, play. I don't," he says. "I walk around with my daughter on my hip and answer e-mail on my two-way."

He gets a lot. His e-mail address is public, and Cuban answers thousands of queries, many imploring his financial aid for, say, organ transplants or guide dogs. "If there is a scenario where the only problem is money, I try to fix that," he says. But Cuban doesn't ever meet his real world beneficiaries. "I'd die if I got emotionally connected," he says. That was an issue on The Benefactor, where, he says, "I got to care about most of the contestants and wanted to make sure I gave the $1 million to the right person." Any hints? Well, let's not forget who this show is all about. Says Cuban: "He or she really reflects a lot of the same principles I have."

Allison Adato. Alicia Dennis in Dallas

  • Contributors:
  • Alicia Dennis.