It's a common fantasy: If you suddenly received a huge pile of money, what would be the first thing you buy? A new hat? A car? A house? A paradise island? All of them, with an NBA team or two on the side?

Even someone like Bill Gates, a man famously sitting on a bigger mountain of cash than some countries, once wrestled with that particular question. As CNBC Make It tells us, the Microsoft mastermind and YouTube superstar had to decide what his first purchase would be when Microsoft went public in March 1986, which gave his stake at the company a market value of a cool $350 million.

He didn't celebrate this with a fleet of new helicopters, or a magnificent 30-course restaurant meal in the most expensive restaurant he could find, though. And as anyone who has ever seen him knows, he certainly didn't buy a nice suit. Instead, he made a financially sound, boring move and treated himself to a debt-free existence by paying off his $150,000 mortgage.

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