Since my move is still a few months out and I don't have any specific plans yet, I haven't spoken to the building dept Mgr, who by the way only posts public office hours for one hour per week!

I did download the town zoning bylaws though and learned a few things:
The plot is zoned "Green Business"
Accessory Dwelling Units are alowable by special permit and only need be 300 sq/ft or greater
Buildings less than 200 sq/ft with no electric/plumbing do not require a permit
Accessory buildings can not be in the required front yard space of the primary dwelling
Accessory buildings must be 1.5X further away from the primary dwelling than it's height
a detached professional office building is allowed with no more than one FT employee that is not a relative(my wife is going for her CPA!)
accessory dwelling units must not be visible from the plot frontage (not a problem here)