I'm also doubtful that anyone could make their living this way outside the San Francisco city limits.
Around here, you'll see fliers posted by people who are willing to do anything for some quick cash. They'll often read something along the lines of . . .
Handyman Available - Carpentry, Roofing, And Some Plumbing Experience. Have Own Tools. Also Available For Lifting, Hauling, And Moving Work. $20 An Hour. You Won't Find A Harder Working Man. Gurunteed.
The content of the flier varies depending on the skill of the person involved, but you get the gist. You'll find them on community bulletin boards, telephone poles, yard signs, tucked under the window wiper of your car in your local parking lot, on and on. This whole system in the article just seems to be a bit more modern and I'm sure the author is probably cherry picking some of the more ridiculous scenarios to try and make a point.
Edit: Of course, hiring these people is at your own risk. They're often not insured and there is little to guarantee the quality of their work.