Here's what Mark Cuban wishes he knew about money in his 20s

Billionaire investor and entrepreneur Mark Cuban is generous with his advice.

He's talked about the best moves for lottery winners, what it's like to become a billionaire (while naked), and how the average person should invest.

He has also shared some important personal-finance advice.

When Business Insider asked him what he wishes he'd known about money in his 20s, he said:

"That credit cards are the worst investment that you can make. That the money I save on interest by not having debt is better than any return I could possibly get by investing that money in the stock market. I thought I would be a stock market genius. Until I wasn't.

"I should have paid off my cards every 30 days."

Cuban zeroed in on some core personal-finance concepts: using credit cards responsibly, staying out of debt, and not fancying yourself a stock market savant. Interestingly, his insight doesn't touch on buying sports teams or the hottest investment of the moment, which just goes to show that no matter who you are, or how rich, the same basic financial guidelines apply.

Find out what other successful people wish they'd known about money in their 20s »