Jack Kerouac would be proud of you!
Like most, I have never been one for the complete vagabond life, preferring ties to home and family. Let's face it most guys into detecting are regular stiffs in search of a little fun. I have however, wandered all over the US and Europe in search of life's grand adventure and did find that if you ARE going to roam in search of adventure - its indeed a good idea to have some way to feed yourself and pay for gas.
Some other ideas that come to mind are painting, lansdcape maintenance, carpentry, home repairs - I have made money at all of these things. No reason why someone else couldn't. Most of the tools one would need for these things could fit in the same space as your stump muncher.
Can you expand a little on your vision of a MD'ers union? We already have the inteconnection of the Internet as a way for us to keep in touch. I know of people al over the country that I could visit, should I take a mind to. And there are "buddy" lists on almost every site as well as other posting forums. What are the benefits that "union members" might gain by participating in your confederation? Are you suggesting a dedicated site for them? I think the FMDAC may already have that covered, as well.