Years later, as he faced the implications of his audacious $800 million bet against sub-prime mortgages, Jeff Greene was to remember that distant day when his father took him to discover vending machines.

Greene, who turns 55 on Thursday, has been a traveling marketer for a small circus, a Harvard business school graduate, a big-time real estate investor, a celebrated Southern California party host who had boxer Mike Tyson as best man at his million-dollar wedding. Now, he’s a billionaire family man in a South Beach condo with his investment company set up in Coral Gables and his 145-foot yacht undergoing repairs in a Miami River boatyard.

The Wall Street Journal called him “The Meltdown Mogul” in a front-page story. Forbes dubbed him “The Reluctant Billionaire.” He’s a major character in the just-published book The Greatest Trade Ever.

But through all this, the formative event in his life was the collapse of his father’s business. When he was growing up in Worcester, Mass., Marshall Greene was a prosperous businessman, buying and selling used textile equipment until New England factories shut down in the 1960s as operations shifted to the cheap-labor South.

“Suddenly, my dad’s business is gone,“ Jeff Greene recalled one afternoon, sprawled on a sofa in his 31st-story apartment overlooking downtown Miami.

His dad moved to West Palm Beach and tried several businesses without success. His mother, until then a stay-at-home mom and Hebrew teacher, took a job as a waitress at The Breakers.

“My mother’s putting on a uniform, and my dad’s in a little warehouse with all these cases of Coke.” His business was driving around and refilling vending machines in motels and such. “It was very sad. Here’s your dad in his 40s, carrying these heavy cases, putting them on the rack, and I’m doing it with him,” at the age of 14.

“That was upsetting to me. I’m thinking `wow, how our fate has changed. My dad is a physical laborer. He used to have people working for him. . . ‘ Of course, that was very motivating for me. I never wanted to be in that position.”

And he hasn’t. Forbes estimated earlier this year that he’s worth $1.3 billion — much of it made in the past several years because he firmly believed that the real estate market had gone nuts. He used complicated financial instruments — the same instruments that caused Wall Street investment bankers to flounder — to short the nation’s mortgages.

But that’s getting ahead of the story.

Greene’s maternal grandfather sold clothing door to door. His paternal grandfather dealt in used textile machinery, and his dad joined that business.

Stephen Becker, a friend since nursery school days, says Greene was always “an ambitious type of guy,” getting extra money from such things as paper routes. Becker and Greene were “very involved in our local temple,” but Greene took things a step further, going to Israel on an exchange program for part of his senior year in high school. He became an expert on blowing the shofar at holiday services.

When his parents moved to Florida, Greene stayed with an aunt in Worcester, to finish high school there, then enrolled at Johns Hopkins University, but he spent holidays and summers in the Sunshine State.

One December, he worked as a bus boy and waiter at The Breakers, the elegant Palm Beach hotel. The next summer, after his freshman year of college, he answered an ad for telephone sales. He went to an office in a downtown West Palm Beach bank building, where he was handed a script selling circus tickets to benefit a local Fraternal Order of Police.