I think that through pool instruction one could make a living.
For example, insert the name of the pro here. The pro is going to the US open. So a few months in advance they schedule lessons all the way on route. Lessons with a top pro could be around $100 per hour with a 2 hour min. They do 2 - 3 lessons on the way every day or so, and make some good cash just going there, and then on the way home the same thing. 400 - 600 per day 14 days there, 14 days back. Nice peice of spending money just there...
Pete