Do any other teachers diversify their income to supplement their paycheck, or is it jut me?

I am a special education teacher for a Title one school in a state that doesn't pay teachers well. I really need to be a teacher because I need health insurance, disability insurance, and the summers off for health reasons, so I started a business on the side to make extra money, and diversify my income in case I am laid off. I have a few clients and I make decent extra money, but it does take a lot of time. Do any other teachers out there do this? How do you feel about it? Do you recommend any books, articles, or websites on the subject? Thank you in advance for your feedback.