A publication I submitted to said that I need to include a biography in the paper. I don't have many formal qualifications, aside from my degree. I have done my research on my own, and am unaffiliated. What can I put in the biography?
I would check a few articles of the journal you publish in and look at what other author are putting in their biography.
Mostly it will be about your degrees (BSc, MSc, PhD, when and where), the field of research you are interested in and what is your current occupation. In summary you can state anything that shows your experitise in the subject you are discussing in the paper.
If no one but yourself paid you for the research, you can state it like:
beside a job as your paying job he/she is working on paper subject
Since date has been working on paper subject