Asked to tutor in a class I am currently taking
Like most things in life, being open and honest is a good policy.

Since you (presumably) are not close friends with this individual, and he is asking for assistance it is reasonable to request compensation as a tutor.  Every person on this planet has finite time and resources.  Having a near stranger request time should result in some kind of compensation, mutual friendship, or you should decline.

You can tell him that you're happy to catch him up to where you are while tutoring him, but if the topic advances faster than your learning, either work through the problems with him at a reduced rate (or free if you feel like it's equal contribution) or simply suggest finding another tutor at that point.