Before I gave anything, I'd go on word of mouth, and probably call up like "I'm calling for a friend" kinda thing. If they've got a dipshit at the reception desk, I'll go no further. Ask a bunch of stupid questions, testing their patience. Very often the people who call such organizations are faced with a problem they've never experienced before, and don't know the proper questions to ask, what the organization actually does, they're just grasping at straws.
The first impression is a lasting impression. If a person who actually needs that help can't get it with legitimate needs, they can kiss my ass.
As far as bums go, I'll give 'em five bucks if they've got a kid hanging around with 'em. I know what a sandwich costs.