Knock on the Door Might Mean Foreclosure

Whether it's on the gritty streets of Bunche Park or in the marbled lobbies of condos on Brickell Avenue, everyone seems to know Seth Gissen -- or at least his kind.

Grim and focused, he is known by the stack of papers under his arm, the way he peers in windows, jots down tag numbers, and queries neighbors or the concierge. When he knocks on the door, it is loud, brisk and authoritative.