Thanks, redpepper. That's some good advice. Sometimes I worry so much about the possibilities when the easiest thing to do is just be natural. Part of the problem is that she doesn't seem to work very often, so I only see her once a week at most.
I'm also concerned about how notoriously shy I am. I'd been about 5 years out of college with only about 3 dates and no relationships when I met my wife, and SHE asked ME out the first time. But it's still a good plan to go slow.
I'm not really the kind of person who NEEDS a poly relationship. My wife and I have done fine together for years. But when I feel a special spark, and the situation seems possible, I'd like to at least look into it.