If you have the budget just get an RV and build a shop inside. Or a toyhauler so you already have work space.
I have a friend who keeps wanting to design a "stealth" RV but the thing I always come back to is how miserable it would be not having windows and such. You're not likely to fool anybody by using a plain white van, probably more likely to get hassled. I've had several campers and with the limited space inside being able to open a window is a necessity IMHO.
As far as I know there isn't any law against using machine tools in public, if you plan on sleeping in it however some municipalities have a problem with that depending on where you are. If it were me I would plan on having something that would be acceptable in an RV campground, maybe even a shop built into a utility trailer that I could pull behind my living quarters. Have you considered how it will be to have all your clothes, food, etc. saturated with the smell of cutting oil?
This is my "shop trailer", sorry just the outside but I have a drill press, generator, compressor, workbench and a bunch of tools inside.
If you built something similar and made things to sell at craft fairs you could call it a business and write it off on your taxes (consult with an accountant of course).
RV parks are pretty pleasant places and I'm sure many wouldn't mind you puttering on your lathe during daylight hours. You would also have a 30 or 50 amp AC service so wouldn't need to run any sort of generator.
Of course I don't know what your two months out of town consist of but your needs might be met in different ways then you're thinking of now....
John