Moving to Mass, Camper/Dually, Commercial License Required?

Each state has those laws a bit different, but in CA commercial registration on vehicle is for revenue-getting purpose and has nothing to do with driver licence requirement.
You can register station wagon as commercial vehicle, what will cost you here in $50 range a year and will allow you parking in commercial zones.
I think it is federal law that you don't need CDL on vehicles up to 26,000 lb and trailers up to 10,000 lb.
RV are exempt from CDL requirement all the way.
Good luck on your move.