Working for free. It is so common issue, among photographers, should you charge every work. You should not charge work that can give you good exposure, full control over results, that you will get images important for your portfolio, and all other different beneficiary things that goes with that imaginary job.
But recently, I did one small job, that didn't fit into any of those categories but, I decided to do it for free. It was about model polaroids. Client insisted to pay but I insisted that it's on me.
One month after it, the model has lost some weight and agency told her that she need new polaroids. Guess what? She didn't come to me. I received a message with content like "I know that you won't charge me , as you didn't last time, so we called another photographer , because we want to pay. "
I believe that it is not necessary to write my attitude now. You can conclude by your own.