It costs money to get a piece of paper that proves you got smarter.
You can go to any public library and get access to nearly published material to learn from for free.
All you're missing now is academia. So go bum around a public university library and ask some college student if they canl check something out for you. Admittedly there's a money piece here, there's way around it, not all of them legal, but that'd be your easiest path.