Dear Academic Publishing,

I'm teaching life sciences, and I have recently started writing a textbook. For now I'm only using it for my classes, but eventually I plan to put it for free somewhere on the web. As I'm teaching this class yearly, in 2-3 years I may actually be able to finish it. In the long-term, I hope to also sell it in a paperback format, really cheap, just to make it a bit more material for those people who like to read books on paper. But I guess it may be a bit too early to think about it at this point.

Nevertheless, I have a question to you that may be relevant already now. How should I deal with illustrations? In my field I need to have lots of illustrations, and most of them originate from scientific papers or reviews. How would I even approach that, from the copyright point of view? I can actually afford to redraw every illustration by hand, as I have experience in that, but would it count as fair use (if the book is free)? Or would I still have to request clearance from the publisher?

And if I need to request clearance, would it possible to get a blanket clearance for the entire publishing house, or would it be on a paper-by-paper basis?

Right now I am obviously using original figures (not even "adapted" or "redrawn") in my classes, which is explicitly covered by the fair use rules, but I was wondering at which point would the rules change: is it the moment I put it on the web, or is it the moment I try to sell the book at cost? And also I'm trying to understand whether there's anything I need to do now to make my life easier later.

Please advise, and thank you!