How To Make Money In Trendy Businesses-And Survive When The Trend Ends It takes a mix of strategy, luck and conviction.

Nate Martin's timing was perfect. "Escape rooms" were having an international moment -- starting with one business in Kyoto, Japan, in 2007, and then rapidly expanding across Asia and Europe. They're like an interactive puzzle: People pay to be locked inside a room and work together to complete a series of tasks in order to "escape." In August 2013, just as the concept was expanding in the U.S., Martin invested $7,000 to build one called Puzzle Break in Seattle, and he made his money back by the end of the year. He then franchised in Long Island and struck a deal with Royal Caribbean to install escape rooms on cruise ships -- grossing $660,000 in 2015, and putting him on track to more than double his revenue in 2016.

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Despite his success, he cautions entrepreneurs against following his lead. "There are now more than a thousand escape rooms, each competing with exponentially larger budgets," he says. "The barrier to entry is rising so fast, no one could get away with what we did."