Every Saturday from 1:30 p.m. to 5:30 p.m., the abandoned Pinckney Community Public Library in the rural town of Pinckney, Michigan flickers to life. Two caravans bearing young professionals in white coats roll up to the parking lot. Once inside, they loop stethoscopes around their necks, shuffle color-coded forms around the front desk, and smooth out paper bed covers on mattresses. One of them swings a sign stamped with the words "Clinic Open" toward the front door. In the cramped back room, a senior medical student is giving a crash course to a second-year on the essentials of heart pharmacology.