When Detroit's semipro soccer team needed a bigger stadium to accommodate its growing fan base, it did something unusual. Instead of seeking tax breaks or subsidies to support its ambitions, it turned to private supporters, mostly fans. It did so with the help of the Michigan Invests Locally Exemption or MILE Act. Detroit City FC raised $741,250 from 527 investors to refurbish Hamtramck’s Keyworth Stadium. The team’s first game at its new home, on May 13, was a sellout with 7,410 tickets sold. That was more than double the 3,500 tickets it was limited to selling when the team played...