If Mark Cuban needed to rebuild his fortune from scratch in six months, starting with just a phone and $500 in cash, he knows exactly what he'd do.

"That is the best question I have ever been asked in my entire adult life," the billionaire entrepreneur and investor told Wired in a recent video Q&A. His first step, he said: Land a sales job, and use one of his best skills to quickly get ahead. It might not even make a difference what product or service he'd be selling.

"I am really, really, really good at sales," Cuban, 65, explained. "I'm going to find a sales job. Because I already know that if I'm down to my last $500, and all I have is a phone, I am going to get that job and I am going to learn more about that industry than anyone on the planet."

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For his first three months, his goal would be to make quick money by by giving himself "a commission as high as I possibly can" on his sales, he said. He'd also try to establish an impressive track record, showcasing his skills, to build future leverage with his bosses, he added.

"Three months in, when I've demonstrated that I am the best salesperson in the history of that company, I'm going to walk into my boss' office and I'm going to tell him or her: 'You're either going to pay me this amount of money to keep me, or I'm going to start my own business selling this stuff,'" Cuban said. "That is exactly what I would do." 

'Everything always goes back to sales'

Cuban's strategy aligns with advice from career experts, who often say there's no wrong time to ask your employer for a raise, as long as you can make a strong case for the value you bring.

"Set up a meeting with your supervisor and bring the previous period's accomplishments, how the supervisor benefited, what the loss would be to the organization if you were no longer part of the team, and what it would cost to replace you and the time lost in doing so," career expert Joe Mullings told CNBC Make It in 2021.

The billionaire's response could also be interpreted as identifying your most valuable skill, and finding a way to monetize it. But that's not exactly the case: There's something particularly valuable about excelling at salesmanship, said Cuban.

Sales skills apply to every area of business and life, Cuban often says — from trying to sell someone a physical product to impressing someone in a job interview or convincing your boss that one of your ideas is worth a shot.

"Everything always goes back to sales, no matter what," he told Wired.

'Selling isn't about convincing, it's about helping'

Cuban has been honing those sales skills for much of his life. When he sold garbage bags door-to-door at age 12, he developed a 14-second sales pitch to explain the value of his business as quickly as possible, he told GQ last year.

The idea was to show his customers he valued their time as much as his own, he said.

"It went like this: 'Hi, my name is Mark. Do you use garbage bags? I've got a great deal for you, and every time you need garbage bags, all you ever have to do is call me and I'll put 'em in the back of my wagon and I'll bring 'em right down to your house,'" said Cuban.

More than a decade later, Cuban used those skills to make a fortune. He founded software company MicroSolutions, which sold to CompuServe in 1990 for $6 million. His next startup, audio streaming company Broadcast.com, was acquired by Yahoo in 1999 for $5.7 billion.

Throughout his career, Cuban has said he's always fallen back on what he considers the first rule of sales: "Selling isn't about convincing, it's about helping," he said in a TikTok interview last year.

"When you understand what people need and want, you put yourself in a position to help them," said Cuban. "Then you make good things happen, close deals and that's how you create companies."

Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank," which features Mark Cuban as a panelist.

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