Mayor Neil M. O’Leary has agreed to sell Green Hub Development the roughly 60,000-square-foot, five-story, “Odd Fellows” building at 36 North Main St. The city claimed it from a New York investor in 2013 for unpaid taxes and utilities. It’s been empty for more than a decade and is in rough shape. At the request of Waterbury officials, the state agreed last September to borrow $10 million to help defray redevelopment costs. Green Hub is the development entity created by New York City financier Louis Forster and his brother-in-law, Joseph Gramando.