Tom Koch, the mayor of Quincy, Massachusetts, is trying to buy the campus that Eastern Nazarene College abandoned when it shuttered last year. With 27 acres in a historic, tree-lined neighborhood close to the coast, the site would be perfect for the Boston suburb to expand its reach — and ensure no commercial developers get their hands on the land. The problem? Quincy would have to borrow $22.5 million from the municipal bond market at a time when its budget is already strained.