When you are preparing your writing resume, do you include work that you have done for free? You should!
The purpose of sending a prospective client your resume is to share some information about your background, education, and work experience. All the writing you have done, whether you have been paid for it or not, is part of your experience, and you should add it to your resume. When someone is considering whether they want to work with you, they care about your experience, not whether you actually got paid.
If you had to write papers in college, then that is writing experience. Many jobs have some element of writing in them, and this is also experience that you can put on a resume. You may have been responsible for contributing to a newsletter for your church or another organization on a volunteer basis, and that counts as writing experience too.
Your resume is not a static document that you prepare once and then you’re done. (Yes, I can hear the collective groan as you read this.) Every so often, you need to review it and make changes as necessary. As you gain experience and have more information to add to the resume, you can update it to focus on your more recent work.
When I was starting out, I wrote for a couple of web sites on a volunteer basis. The experience gave me some samples to show to prospective clients. I still list them on my resume and no one has asked whether (or how much) I got paid for writing them.
Do you include paid and non-paid writing on your resume or do you list paid work only?