gkp, I've been interested in doing this also. I did help one friend but didn't charge her. I was like you...unsure of what to charge. A flat fee doesn't sound right since some people needs LOTS more help than others.
I did notice that it would probably be better to just guide someone rather than do it for them. If they don't learn, they won't keep it up. An hourly rate with a set consultation fee would probably work best.
I didn't know there were any more of "us" out there.

I love to organize too & do just what you do with the closets.