I work 3 weekends a month where I board, for an astonishing $75/day off my board. Considering I handle, feed, turn out/in, and clean stalls for 10 horses - all of which takes maybe 2hr 15min (1hr 30min AM and 45min PM) each day - yea, I'm totally making out! I'm the first person my BOs have had work off board. I believe they realized very quickly how great it was to have time away from their duties, all the while knowing that they could trust me and my abilities completely.
As for how to find people like me, I second the Craigslist thought! I see ads on our local CL often for people looking to work off board. Always important to do a trial run and set all expectations up front immediately.