I agree, we are allowed to sell 4 guns a year in Mass, buy hundreds but only sell 4. However if we go through a dealer or sell to an out of state dealer we can sell as many as we want. Selling to an out of state dealer the paperwork is easy.
Selling through a dealer in Mass most charge 20% of the sale. I did that with my Bushmaster and an Armi Jaeger AP74, but want to put some C&R guns up for a good price and they may take a while to sell and most dealers don't want to do that, it is all about turnover (as well as the 20% commission).

I am pretty sure that I can send to a 03 (03 to 03) but want to be sure.