There's a fine line between pitching in to help someone and working for them for nothing. Sounds, as many people have pointed out, that you're on the wrong side

There's a fine line between pitching in to help someone and working for them for nothing. Sounds, as many people have pointed out, that you're on the wrong side of that line. The next time you're asked to help, ask them where you send the invoice. Or lay out some terms of engagement - what you will and won't do, how many hours you'll work, the hourly fee you're expecting, payment terms, and reasonable travel expenses (if any travel is involved). Yes, that will probably turn a lot of people away, but if they're making money from your time and effort shouldn't you?