Doubtful you'll find actual free current textbooks. You can probably find pretty cheap older editions. And you can most likely find MANY websites dedicated to the topic.
I didn't say you can't get things for free. I said that it is doubtful you can find a free *current* version of a textbook... short of some idiot having paid a lot of money for it and deciding to give it away, or someone angry with the company who scans it and posts it, risking being sued. All sorts of free stuff... but not current textbooks.
I'm not sure. There may be if you have a specific textbook in mind. There is also the option of renting textbooks so you don't have to buy them.
Tell me the names of the books and I'ld gladly help you out :)
Just look for ebooks online easy as that