Stefan Qin was just 19 when he claimed to have the secret to cryptocurrency trading. Buoyed with youthful confidence, Qin, a self-proclaimed math prodigy from Australia, dropped out of college in 2016 to start a hedge fund in New York he called Virgil Capital. He told potential clients he had developed an algorithm called Tenjin to monitor cryptocurrency exchanges around the world to seize on price fluctuations. A little more than a year after it started, he bragged the fund had returned 500%, a claim that produced a flurry of new money from investors. He became so flush with cash, Qin signed a lease in September 2019 for a $23,000-a-month apartment in 50 West, a 64-story luxury condo building in the financial district with expansive views of lower Manhattan as well as a pool, sauna, steam room, hot tub and golf simulator.