@Deceth, that's a very perfect and interesting advice. Though, it would take ALOT of effort to properly create such a product. But if you do it right, it's really worth it.
Yeah i actually agree with Deceth! Since you've obviously got a following/people who trust your site and go to it for math tips and whatnot, you're in a pretty good position to start formulating a product that you could charge a fee for. Math textbooks are an option, but there are lots of textbooks to turn to elsewhere so that might be a deterrent. How about making your own quizzes? Since you have math notes, why not form your own quizzes and charge a minimal fee for users to test themselves on it? After all, the cruz of learning comes from practice and being tested. From the occasional rare textbook that comes with an online testbank, all the other students in my cohort go nuts over it, testing and retesting themselves on it to ensure they've got a clear idea of textbook material. Memorizing and making your own notes only gets you so far. You can even go for it in a more extensive version: test papers. Math is about practice and papers with answers, for students to practise can come pretty high in demand.