Everything comes easy to Mark Cuban, or at least it seems that way. Taking M.B.A.-level courses on the sly as a freshman at Indiana University–easy. Turning a buddy’s idle complaint (“Why can’t we listen to Hoosiers basketball over the Internet?”) into the $5.7 billion Broadcast.com and getting out before the bubble burst–easy. Buying one of the NBA’s doormat franchises and, 16 months later, steering it into the playoffs for the first time in 11 years–way, way too easy. But is it really? Heck, no. Cuban works like a dog. He has the rare ability, though, to master in months what it takes extremely smart people a lifetime to learn. And in the high-profile world of the NBA, sometimes that doesn’t go over too well.

Which is why one big-city columnist has labeled Cuban “an attention-starved rich kid.” And, in part, why NBA Commissioner David Stern calls him a “dream and nightmare”: “The same intensity he brings to his team makes him impatient with the league.” Says Cuban, “I just question processes.”

His favorite target is the “process” of NBA ownership. Cuban does all of the following things that aging, disinterested owners, as a general rule, do not do: (1) goes to every game; (2) screams like mad; (3) talks to the media and (4) appears to enjoy it; (5) welcomes fan e-mail and answers every last one, usually within hours, and (6) says whatever’s on his mind, even when NBA officiating is what’s on his mind. The last one particularly irks Stern, whose office has fined Cuban seven times for $500,000 this season, including $100,000 last week for making a “derogatory gesture” at the refs. But it’s those first five that scare owners–plus one more: Cuban treats his players very, very well.

It’s late afternoon and Cuban is stretched out, feet on his desk, in his cubicle at the Mavs’s sales pavilion. (Cuban does not have an office. He also sits closer to the door than the receptionist.) He is explaining why he treats millionaire athletes like real people. “It’s easy to rationalize: ‘Look how much money these guys make!’ But if you’re seven feet tall and sleeping on a tiny bed and you can’t get room service because your plane landed at 3 a.m., you’re not gonna feel respected,” he says, taking a slug from his Diet Coke. “Guys in the NBA are no different than you and me.” So Cuban upgraded the team to nicer hotels. And put a PlayStation, a DVD player and a flat-screen TV in every locker. And bought fluffier towels for the showers.

Not that Cuban is an altruist. He knows each home game means that another team, loaded with future free agents, comes into his arena, talks to his players and sees how they’re treated. “That dog,” says Philadelphia 76ers owner Pat Croce, laughing. “We’re down in Dallas, and in our locker room there’s pictures all over the wall of their brand-new arena [opening in July]. In the visitors’ locker room! Can you believe that dog?”

Cuban’s smartest move, however, was one he didn’t make. When he arrived last January, the Mavs had a solid foundation already in place: all-star Michael Finley, seven-footer Dirk Nowitzki and rugged point guard Steve Nash. But the team, under coach Don Nelson, was just 9-23. Instead of firing Nelson, Cuban told him to have more fun. “Look, I’m not a basketball expert,” Cuban explains. “I’m not dumb enough to think I know half as much as Nellie’s forgotten in the last 10 minutes.” What he did have to offer was his fire. Every person you speak to uses the same word to describe Cuban, leaving you to wonder if he got to them an hour before you did. Pat Croce: “I love his passion for the game.” Juwan Howard, Mavs forward: “You can tell how passionate he is.” Joe Maloof, Sacramento Kings co-owner: “It’s his passion.” Steve Nash: “He’s just so passionate.”

Basketball and business have been Cuban’s twin passions from day one. Raised in Pittsburgh, he first went into business selling garbage bags door to door. He was 12. Dad upholstered cars for a living; Mom sold real estate part time. “Middle class. Ranch house. It was as normal as normal could be,” Cuban says, hinting that there’s little to be mined from his childhood. His parents told him to work hard, so he did. They told him to think big, so he did. Simple as that.

Cuban, who has a long-term girlfriend, became a billionaire in 1996 after selling Broadcast.com to Yahoo! But it didn’t occur to him to buy his beloved Mavs until the 1999 season opener. “There was hardly any energy in the arena. And I thought, ‘Man, I could do better than this.’ Then it dawned on me: I could afford it!” Three months later the Mavs were his for $280 million. Every sports fan thinks he can do better; Cuban might be the first to actually prove it. And he’s making it look easy.