How do you guys go about collaborating with people you know?

Sup guys, I've been around a while and finally starting to see how the system works and how I should start behaving accordingly. I've put my work in and done enough stuff for free to where I think I can start charging people, but now that I'm getting into the local scene of music I'm stuck on if I'm supposed to charge for it. How do you guys go about collaborating with people that you will both benefit each other? And am I being greedy with this crossroads I've come across