Billionaire Mark Cuban built his career using advice his dad gave him at age 14: Time is your most valuable asset.

For much of his Cuban's childhood, his dad Norton worked 60 hours per week for a company that upholstered cars outside of Pittsburgh, Cuban tells CNBC Make It. Sometimes, his dad brought him along to sweep floors — and, more specifically, show him the limits of working for someone else.

"This time wasn't spent to learn about what my dad did, but to learn that his job didn't have a future," says Cuban, 65. "His time was never his own ... he wanted me to create my own path."

The lesson helped motivate Cuban to prioritize entrepreneurial opportunities over seeking out high-salaried jobs.

"I wanted to make enough money so I didn't have to respond to anybody else," Cuban said in a MasterClass course released last week. "I could make my own schedule and live my own life the way I wanted to do it."

Pursuing time before money

Other lessons from his dad stuck with Cuban, too. When he was 12, his dad told him that if he wanted new sneakers, he'd have to save up. So he bought $3 boxes of trash bags from a friend, and sold them to neighbors for $6, Cuban told GQ Magazine in 2022.

Cuban ran at least two more side hustles, selling stamps and coins, before graduating high school. While at Indiana University, he charged $25 per hour to teach disco dancing lessons. He bootstrapped that cash, with funds from other side hustles, to open a bar with a friend.

After Cuban graduated and the bar got shut down for underage drinking, he moved to Dallas, where — after working for a PC software retailer for nine months — he eventually started his first company, MicroSolutions.

He sold MicroSolutions to CompuServe for $6 million in 1990. "What it bought me was freedom," Cuban told GQ.

Cuban's time-saving email habit

Cuban became a billionaire four years later, when his next company Broadcast.com was acquired by Yahoo for $5.7 billion in stock in 1999. Today, he splits his time between his family, helping run the NBA's Dallas Mavericks — which he co-owns — appearing on ABC's "Shark Tank" and running his pharmaceutical company, Cost Plus Drugs.

His father's advice is still ever-present in his life. Each morning, Cuban wakes up and spends an hour responding to emails on his phone, he told comedian Trevor Noah on a recent episode of the "What Now?" podcast. His work and media communications all go through his email so he can cut out time-wasting phone calls, he noted.

"The whole value of being in this position is just being able to control your time," Cuban said. "It's the one asset you can't control [in typical jobs]."

Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."

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