I would love to guide while I do grad school and I certainly have the time, especially during the weekends, but I don't have nearly enough experience with fly fishing or the fishery I live near. Get back to me in ten years and maybe I'll give you a better answer
For those interested in guiding, Tom Rosenbauer just did a podcast on getting into guiding and the life of a guide, its one of the Orvis News blog podcasts and its certainly informative. I may try to get a job for a bit of the summer working at a saltwater outfitters near my parents' home just to get more experience on the water and with fly fishing. I've been fishing since before I can remember but I don't think I'm to the point yet where I could be a guide skill-wise, and in particular, I don't know my specific fishery well enough as I just moved to WNY. You really have to know the waters you will be guiding on backward, forward, and sideways in order to start taking clients out as far as I've heard. Taking my friends out to catch fish is one thing, taking clients is a whole different story.
There are quite a few guides here on the forum, pick their brains as much as you can