When the refrigeration system failed at an ice rink outside Kalamazoo, Michigan, last September, the Kalamazoo Optimist Hockey Association—whose club had skated there for six decades—was suddenly without a home rink. A month later, a private investment firm bought the building for $3.5 million and promised to reopen it. No local buyer could have moved that quickly. KOHA is a nonprofit with two full-time employees that serves 600 families and nea…