A recent Friday, 12:28 p.m.: Well after downing a cup of coffee, Zach Houston can’t peck out the next line of a new poem fast enough on his 1967 “glow-in-the-dark-green” Hermes typewriter. The caffeine amplifies a thought process that is already frenetic. Writer’s block has never been an issue for Houston, who says he finds inspiration in just about everything. He comes up with poems for people who pass by one of his regular perches in the city — he asks for donations — but he also has thousands of others at home that he never intended for anyone but himself.