As a master plumber, you should have no problems finding work in RV parks. If you go that route, you should also be prepared to do lots of other things (weedeating, painting, site escort, etc). You'll probably make more than minimum wage, but not much more. You may have a better shot at choice locations.
If you just want to be a traveling plumber, I wouldn't think that would work too well. Aside from initial availability, who wants a plumber who may be gone in 2 weeks when/if the repair breaks? You could also run into problems with local licensing.