I started making money online when I was 13 years of age. Mainly, trying to earn some "pocket money" to help pay for presents on special occasions like the Birthdays of my parents, and something left over to treat myself to some snacks at the end of the week; for example. I started by completing online surveys, and I was only rewarded with 1USD$ for a survey completion that took an hour! A few years into this, I then moved on to selling my writing services and eventually became a successful forum owner. I think that as you are dedicating time to you studies, and you are not comprising them, there is no minimum age to start making money online.