Ok, I have started to answer and changed my mind three times already. I guess, when I boil it all down, what I really love about art is that it makes me smile. I have also enjoyed following Flash Mobs over the years. So I think if it were possible to make a living this way I would want to combine these two ideas: Smiling and Flash mobs!
I would create massive works that would incorporate humor and rhetoric and a hint of a crop-circle mentality. All the pieces would be installed in a very public areas and viewers would have no idea how or when they got there, and I would document the visitors who stopped to enjoy the work. (which eventually, I think, might become another installation.)
Whenever possible I would try to add something to the work that encourages the viewer to get involved so that the piece would change and morph into something completely different from where it started. After all, isn't that what we are all doing every day?
That seems like a wonderful way to make a living and something I would love to do.