I have been using codementor.io and I love it. It is similar, except that you get paid to teaching instead of having to pay to teach. That one is for you in cas

I have been using codementor.io and I love it. It is similar, except that you get paid to teaching instead of having to pay to teach. That one is for you in case you are interested to keep growing (and get some money). For your friend I think that is great as you avoided any kind of conflict of interests for him.