If you're a real teacher I'll pay you for the practice. But I tend to shy away from "free help" because then people can schedule times with me, not show up, and then I can't complain because it's free.
I would rather pay and obligate you to be on time and to help. I can speak Mandarin and so I can help with English for free, but if you are a no-show just one time then you get cut off.
Think it over.