How do you make a billion dollars by accident? Ask friends Michael Meldman, Rande Gerber, and yes, George Clooney. Their tequila company, Casamigos, was formed to satisfying the sublime palate of two friends, with Meldman joining them later in the venture-more on that in a moment.

Let's start from the beginning, Clooney and Gerber were spending some time in Mexico...drinking quite a lot of tequila. Yet they couldn't find the ideal tequila to suit their tastes. One day Clooney asked Gerber why they didn't just come up with the perfect recipe themselves. And that just what they did. For the first two years of production, no one tastes the tequila except for the friends and their families. Later when the friends began getting orders for more than a thousand bottles a year, they found out they needed to get a commercial license. That's when Meldman joined the friends, and started selling Casamigos on a massive scale in 2013. The three partners had massive success, doubling their sales the next year and in 2015 sales were five times greater than two years before. It wasn't long before Diageo (DEO  ), the company behind Guinness and Johnny Walker, took notice. The company paid more than $700 million for Casamigos, with $300 million to be paid based on sales over the next ten years. 

George Clooney isn't the only international star in the business world. Andres Iniesta, the Spanish soccer star, is also in the alcohol business. But rather than tequila, Iniesta is in the wine business with his father. Their company Bodega Iniesta produces wines that allude to Andres Iniesta's success, such as Finca El Carril 166 Blanco, which refers the goal that won Spain the 2010 World Championship (scored at the 116th minute, final score: 1-0). 

But it's not just the alcohol business that celebrities invest in. In 2015, Leonardo DiCaprio invested in Diamond Foundry, which produces synthetic diamonds. DiCaprio is a well-known environmental activist as well as a world-famous actor, known for promoting the protection of our natural resources. Interestingly, he also acted in the movie Blood Diamond (2006), which showed the natural and human dangers associated with traditional diamond mining.

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Of course these are not the only instances of actors becoming investors. So why celebrities, who are already well-paid, venture into business? The first and most obvious answer is to grow and protect their wealth, but there is also the appeal of making something all your own, whether that's tequila or diamonds. And then, some investors become celebrities because of their businesses instead of the other way around, like Mark Cuban, successful businessman turned celebrity and TV star.