Anyone teaching in a park, home, garage or similar for donations only?

I'm wondering how it works out for you? I've taken Tai Chi in a parking garage for donation. With the economy the way it is how do you avoid having a class full of non-donating students?

Obviously I'm considering doing this (to make a few dollars). I've had neighbor's in the past wanting me to teach their kids. The best I could do now would be very informal class but asking for a donation for my time.

Thoughts?