Self-made billionaire Tilman Fertitta shares his best advice for 20-somethings

A brilliant idea doesn't make a successful business. Accounting does.

That's according to Tilman Fertitta, the self-made billionaire and star of CNBC's " Billion Dollar Buyer ." Now worth about $3 billion , Fertitta started by peeling shrimp in the back of his father's restaurant in Galveston, Texas.

In an interview with CNBC, Fertitta says the one piece of advice he would give to every young, 20-something entrepreneur is: "Don't ever let your business get ahead of the financial side of your business. Accounting, accounting, accounting. Know your numbers."

Fertitta's been on top of his numbers for a long time. He launched his career with a $6,000 loan from the bank . Today, the 59-year-old is the CEO and sole shareholder of Landry's, which owns Bubba Gump Shrimp Co., Morton's The Steakhouse, and the Rainforest Cafe.

"Most entrepreneurs come up with a product or they come up with an idea and they think they can be successful with it," he says. "But if they don't know the financial side of their business and understand credit and working capital and what it takes money-wise, you can't be successful. The product is just a product."

The bottom line? "You better know the business side of this product," says Fertitta.

CNBC's " Billion Dollar Buyer " airs Tuesdays at 10 p.m. ET.