This has been my primary source of income for the past 8 years:
http://www.biodieselhauling.org/I charge $40 an hour, but then again, I have a truck.
The majority of my first time clients come from Craigslist (starting to get more from Yelp), though the majority of jobs overall are repeats and referrals.
I strongly disagree with the health insurance comment (not that you shouldn't have it anyway).
People who hurt their backs are people who DON'T do regular strenuous activity. It leaves you weak and soft and vulnerable the times it occasionally can't be avoided.
Also chiropractic is a scam (albeit one with sincere believers doing the hawking - kind of like priests).
Doing real work consistently, especially with aging, is the best way to keep strong muscles and bones, which is what keeps you from getting hurt.