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Barbara Corcoran worked 22 jobs before age 23—here's the one she learned most from

"Shark Tank" star Barbara Corcoran was born and raised in the factory town of Edgewater, New Jersey, where she and her nine siblings all shared a room in her parents' two-bedroom flat. To make ends meet, "we all had to contribute," the self-made millionaire, who made her fortune in real estate, tells journalist Farnoosh Torabi for CNBC Make It. "We all had to hustle."

By age 23, Corcoran had already worked 22 jobs. And she got more out of one particular job than the rest: waiting tables.

"You learn more in waitressing than you can in any other job, and I had every kind of menial job you can imagine," Corcoran says. "What's great about being a waitress is you have your own territory. It's your responsibility. It's your table. It's your counter. The sugar's got to be filled. The ketchup's got to be topped off."

Being a server is "the best way to learn about sales," she says.

Barbara Corcoran attends the premiere of ABC's 'Shark Tank' Season 9
Rodin Eckenroth | Getty Images
Barbara Corcoran attends the premiere of ABC's 'Shark Tank' Season 9

"It's your charm, it's the ability to have a conversation and get the coffee right away so they don't have to ask for it. It's knowing what they ordered last time," she says. That kind of attention to detail "wins people over."

Corcoran actually met the man who would nudge her to explore real estate sales while working in a diner. He even lent her $1,000 to start her own firm, a loan that she would turn into a $66 million real estate empire.

And of the 22 menial jobs she worked in her teens and early 20s, it was waitressing that most prepared her to build a successful company, she says.

"The best job you could have to prepare for entrepreneurship is, walk on the other side of the counter and serve people," Corcoran tells Torabi. "Make them happy. If you've got that ability … chances are good you're going to be a good entrepreneur."

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Video by Mary Stevens