More times than not, when you are in a position of limited knowledge but have lots of enthusiasm to learn, you are not going to get paid for offering your services. In my opinion, and it is only my opinion, there is nothing wrong with offering your time in exchange for knowledge from someone else. You are giving them an extra pair of hands and hopefully making their life a little easier that day, and in return, you are learning. There is an exchange of commodities here, but neither involves money.