Seek low-paying publications. That way you may not be intimidated by large
publications, and still receive payment.
Write articles on your own, and use them as samples to show to editors
when appropriate.
Self-publish an e-book, novel, or other type of book. There are websites
that will place your self-published book for sale.
Research publishers that hire authors to write about an already planned
topic, and send in a proposal.
Write your book now, and send proposals to publishers.
Write marketing material for yourself such as brochures, website content,
fliers, etc.
Write essays, and send the full manuscript to paying publications.
Write query letters and send them to paying publications.
I do believe that there are times when it's okay to write for free. Writing
for non-profit organizations, and for publicity are honorable ways to write for
free. If you really feel that you must give your work away, give it to a
non-profit organization of your choice. If you have written books, write
articles on topics relative to them, and let others reprint them. The bottom
line is that, no, you do not have to write for free to break into freelance
writing!