This is more towards students but anyone can do it. If you have knowledge in a certain area and want to help others pass tests and gain extra knowledge on a subject then you can provide a tutoring service at $15-20 an hour. Another thing that somewhat ties into this is doing other peoples' homework. If you like doing homework then you should definitely do this. You can also download an app called "Socratic." It's a great app, I recommend it to everyone that needs help on homework