Many years ago a certain well-known science fiction author wrote somewhere that authors should never sell their works for "free." According to that author, even getting paid less than the pro rate was about the same as giving your work away. I don't quite agree with this, even though when I send out my short stories I only do so to publications that pay.
For one thing, getting paid in contributors' copies is still getting paid. Those copies have value; otherwise the publisher would be giving them away. For another thing, I've always believed that it's better to sell your work and get the credit rather than wait to sell to a market that pays pro rates. Some markets that pay token payments have been around for a good long time; selling to them can pay off in ways other than a check or PayPal deposit.
Something else occurred to me about this subject. Unless you have a contract, you're writing for free anyway. You're writing your book, short story, or article with no expectation of getting paid, but in the hope that your work will sell to a paying market.
What about blogging? Unless you're charging readers to see your blog, that's writing for free. Of course, most writers blog in part to promote their writing. In that way blogging isn't free, but a promotional tool like a press release that you write to get other things to sell.
While it's good to write with the idea that you'd like to be paid, you need to have something to say first. You need the passion to write, and the passion to be heard. The one will get you working; the other is what motivates you to sell what you write. Where you sell, and how much you're paid, are your own decisions. As long as you're comfortable, you shouldn't worry about what others think.
Write what you can and sell where you can. After all, you can choose where you submit your work to, but someone else decides whether or not to publish it.