My business model is selling online courses, not affiliate marketing.
However, there’s nothing wrong in allowing your audience to reward you a little for recommending stuff they might find useful.
So I occasionally use affiliate links. They’re links that if you click and later go on to buy that product, I get a little commission payment. You don’t pay any more than you would have anyway.
Two things you need to know:
One: I’m strictly only ever an affiliate for stuff I personally own, and love, and use regularly.
Two: I’ll always do my best to flag up the fact that a link is an affiliate link.