I've been interested in trying Craigslist as well. I wonder what would happen if you offered to let their kids/family join you? Basically, make the ad be more like an invitation for a "treasure hunt" on their property. I could bring along a few extra detectors and tell them that I would give them instructions on how to use them for free. It could be an enjoyable afternoon for a family and you'd be building good will. You might get the kids involved in the hobby and if they really enjoy themselves they are likely to tell their friends and neighbors about how much fun it was which would lead to more calls.
Heck, you could even end up doing birthday parties and such. You could run an ad for a treasure hunting party. Imagine being paid to bring 10 detectors and entertaining a group of kids for a couple of hours. You could seed the lawn with some cheap foreign coins to make sure that everyone finds something. The ultimate would be to setup an actual treasure map and lead the kids to a small cache. Once you'd built up a "shtick" it would be easy to just carbon copy it over and over again. If the kids have alot of fun it could lead to a lot of side gigs and open up opportunities to hunt areas based solely on your reputation.
Just something I've been thinking about. I really like the idea of using CL and I think if you were creative about it you could probably open up a lot of opportunities. Some of which could even lead to being paid to hunt.