You can give away 100 dollars, as a dollar each to anyone who asks you for change, for a week straight.
When you go broke, you can ask 10 people for a nickle, for three days straight. And when they all say no, remember that that's their character, not yours.
That's not your karma. That's their intention.
Keep your intention while receiving their treatment. God forbid you have to deal with a selfish man's karma.
Give when you have. When you can or when you want. Let them be selfish. And give when you have.