Barbara Corcoran doesn't believe in letting cash sit idly.
The entrepreneur and longtime investor on ABC's "Shark Tank" says "money is meant to be spent" — but only in a handful of places.
"One piece of advice people hear all the time, and I just don't believe it, is: 'Diversify, don't put all your eggs in one basket,'" Corcoran, 74, tells CNBC Make It. "I put all my money in the real estate basket, my brokerage firm, and everything in there went to buying properties."
"I spent every dollar I ever made and threw it back into the business," she adds.
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Corcoran says she's built "a lot of wealth" by investing carefully and watching the market, but not worrying about investing in across different industries. She sticks to buying and selling real estate — an industry she knows well, after creating real estate firm The Corcoran Group in 1973 and selling it for $66 million in 2001 — instead of venturing into areas like tech or health care stocks.
In a way, her advice echoes Berkshire Hathaway CEO and chairman Warren Buffett's famous investment strategy, which is to only invest in companies that you believe in. Currently, Berkshire Hathaway's equity portfolio focuses on only five stocks, according to its annual report: Apple, Bank of America, Chevron, Coca-Cola and American Express.
Berkshire Hathaway's decades of investing success are largely responsible for Buffett's current net worth — $104 billion, according to Forbes.
Tesla, SpaceX and Twitter CEO Elon Musk, currently the world's second-richest person, employs a similar approach. "Buy stock in several companies that make products [and] services that you believe in," Musk, whose net worth is $191.4 billion, tweeted last year. "Only sell if you think their products [and] services are trending worse."
The difference: While Buffett and Musk focus on stocks that can span multiple industries, Corcoran focuses on a narrow set of physical goods, like houses and apartment buildings. She specifically recommends the real estate approach for young people looking to invest, even if means asking their families for financial help at first.
"You have to get in the game because when you want your one-bedroom, you need a chip to trade up with [for] when you want a two-bedroom apartment in the suburbs," Corcoran told the "Chicks in the Office" podcast in March. "Forget about the timing [of the market] ... [Get in] right now."
Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."
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