For nearly 30 years, John Hayden and Keith Pryor have lived a block away from a small structure with boarded-up windows, crumbling brick and a link to the Beat Generation. “You walk by it every day and think what that might be,” Hayden said. The building at 2558 Champa St. has been on Denver’s formal list of “neglected and derelict” buildings — which are considered unsafe, a nuisance or habitually in violation of city codes — since 1999.