Mark Cuban sold his company to Yahoo for $5.7B in 1999. He then made a Wall Street trade that protected his billion-dollar fortune before the dot-com crash. Another man kept every share of stock he owned. When the market collapsed, he had to sell the house he'd spent $25M building. Cuban bought it for $12.5M. Here's what happened. In 1999, Cuban and his business partner Todd Wagner sold Broadcast com to Yahoo in one of the biggest internet acquisitions of the decade. But Yahoo didn't pay them in cash. It paid $5.7B in Yahoo stock. Cuban's stake made him a billionaire, but his fortune was now tied to a single company whose stock price had been soaring. He knew how quickly that could change. So instead of betting everything on Yahoo continuing to rise, he worked out a way to protect his shares. The strategy was called a collar. He sold call options, giving other investors the right to buy his shares above a certain price. He used that money to buy put options, protecting himself if Yahoo's stock fell below a certain level. The trade had 2 consequences. If Yahoo kept rising, Cuban would give up some of the additional profit. If Yahoo crashed, his downside was limited. He was willing to sacrifice potential gains to protect the fortune he'd already made. Then the dot-com bubble burst in 2000. Yahoo's shares eventually lost more than 90% of their value from their peak. Cuban's hedge protected his wealth. But another investor wasn't so fortunate. He had spent 3 years and roughly $25M building a dream home for his family. They lived there for just 8 months. When the stock market crashed, he had never sold a share of his stock. He had to sell the house. Cuban received a call offering him the property for $12.5M. He bought it without ever visiting. The man who protected his stock market fortune ended up buying a home for half its construction cost from someone who hadn't protected his. Cuban later explained his thinking in an interview: "I was worth a billion dollars. How much money do you need?"