The first time Ulysses “Junior” Bridgeman learned how the smart money thinks was over breakfast at the Hyatt Regency in Oakland with former Milwaukee Bucks owner Jim Fitzgerald.

It was the early 1980s, and Bridgeman was then the team’s super sixth man—a clutch sub who rarely started but who would eventually play in more games for the Bucks (711) than any other player in history. Bridgeman was scanning the sports section in the local paper as Fitzgerald, sitting across from him, pored over stock tables in the Wall Street Journal. Casually the 6-foot-5 athlete revealed his desire to “get involved in something in the business world,” he recalls—to which Fitzgerald replied, “If you get involved with business, you only have two problems: people and money.”

Bridgeman, now 60, didn’t quite get the punch line at the time. That type of humor just wasn’t the sort he’d grown up with. In his hometown of East Chicago, Ind., the country’s largest steel mill was the dominant industry, occupying much of the Lake Michigan coast. Two generations of Bridgemans had worked there, but Junior’s father, Ulysses, was determined that his second-born (and namesake) would keep his nose in his books and find a life beyond steel.

Early on, Bridgeman did just that—proving to be a better student, initially, than he was a student athlete. “There was nothing growing up in my life through that time that indicated I’d get a basketball scholarship,” he says. But by his senior year at Washington High, Bridgeman was helping to lead his school to a 29–0 season and the 1971 Indiana state championship. The University of Louisville offered him a scholarship, and he grabbed it, helping to bring that team to a berth in the 1975 Final Four his senior year. Off the court, Bridgeman kept to his books, studying for the LSAT and completing a degree in psychology. But when the Lakers selected him with the eighth pick in the draft, plans for everything else fell away.

A week later the Lakers shipped Bridgeman and three other players to Milwaukee in exchange for Kareem Abdul-Jabbar, by then a four-time reigning MVP. The loss of Kareem (and the retirement of the Bucks’ All-Star Oscar Robertson) didn’t open a spot for the newcomer in the starting lineup, however. Instead, Bridgeman settled in as the sixth man on the Milwaukee roster—eventually posting 13.6 points over an average 25 minutes of court time. “Junior knew what his role was as soon as he stepped into the game,” recalls Harvey Catchings, a teammate on the Bucks and, later, the Clippers. “He provided offense, moved the ball, got a few rebounds, got a few assists.”

He was equally adept in his role as an officer and then president of the NBA Players Association, where the small forward/shooting guard got his first real taste of the business world. In meetings there would be heated debates about salaries and travel per diems—“the most important thing in the world to us players,” he says—but the owners, it seemed to Bridgeman, were far more concerned with their business deals outside the NBA. The years he spent haggling with them turned out to be more valuable than a stint in B-school. “Just watching the owners’ thought processes—they were two or three questions ahead,” he says. “It was an unbelievable education.”

From there, though, the learning curve got steeper. The NBA in Bridgeman’s era was light years away from today’s age of big money. Non-superstars like him didn’t get rich from player salaries and endorsements. So during the off-season, he sold insurance at a local firm and worked the front desk at a Howard Johnson. “It was a major adjustment,” he says, “to have to be somewhere all day with a shirt and tie on, filling out forms or answering the phone or checking people in.”

Junior Bridgeman Milwaukee Bucks 1983Junior’s league: In a jersey the Milwaukee Bucks would one day retire, Bridgeman (No. 2) drives to the paint against the Celtics’ Charles Bradley at the Boston Garden in 1983.

The hours didn’t get any easier after Bridgeman began working for himself, after retiring at age 33 in 1987. Seizing on a love of hamburgers, Bridgeman bought five Milwaukee-area Wendy’s WEN franchises. He insisted on working in every facet of the business, from flipping burgers to mopping the floors—to the point where it was often hard for an outsider to tell who was the boss. Once while working the line at a restaurant, he could feel a woman regarding him quizzically, as if trying to figure out where she knew him from. The next day, Bridgeman was listening to a local radio talk show when a caller broke in: “I was at Wendy’s, and I saw Junior Bridgeman working behind the counter,” the woman groused. “If that’s the best these ex-athletes can do …”

The truth was, even as the owner, Bridgeman was doing only modestly. His best store brought in $800,000 a year in sales; his worst, about $400,000. The baseline for a Wendy’s in the Milwaukee area was then about $850,000. “A lot of people may say the risk didn’t make a lot of sense,” he says, “but at that point you have to make it work anyway. Failure was not an option.”

The first step for the burgeoning franchisee was to reject the notion that Wendy’s burgers would sell themselves: It was up to people to sell them. So he hired better workers and empowered them. “What I tried to do was to get everybody to understand that we were a team,” he says. “We worked together as a team, we win as a team, and we lose as a team. Once everybody bought in and believed that we could be successful, it was amazing how quickly things started to improve.”

Today those restaurants, which bring in more than $1.5 million of annual sales apiece, are at the heart of a 195-store portfolio—making Bridgeman’s private company, Bridgeman Foods, America’s second-largest Wendy’s franchise owner. (Bridgeman won’t discuss his profits.) He also owns 125 Chili’s restaurants, 45 Fannie May Chocolate stores, and scads of other retail franchises, most of them clustered in the upper Midwest, between corporate headquarters in Milwaukee and Louisville. His employee roster numbers 9,000 people. Estimates of his net worth range from $250 million to $400 million.

Bridgeman, meanwhile, has been an eager mentor to NBA players who express interest in putting some skin in a totally new game—teaming up last year, for example, with Pistons guard Chauncey Billups to buy 30 more Wendy’s restaurants in the St. Louis area.

For every player like Billups, though, there are several more who end up going broke within five years of retirement—tales that break Bridgeman’s heart. “Unless you grew up in a family where someone owned a business or you sat around the kitchen table talking about the business page—which 99.9% of the players didn’t—you have no idea what $10,000 or $100,000 can do or how long it really lasts,” he says.

After some 27 years in business, Junior Bridgeman can safely say he knows the answer to both.

WATCH: Trading baskets for burgers: The Junior Bridgeman story

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This story is from the July 21, 2014 issue of Fortune.