Wow, sorry it's a hassle wherever you live, registration of a home-built trailer in NY is really simple. You get the trailer weighed, take your weight slip and your parts receipts to the DMV, fill out a form, pay the fee and you're done. Along the way they ask you what you want the weight rating to be, and they put whatever number you give them on the registration document. They didn't even look at my receipts when I did the yellow trailer. Once that's all done you get it inspected at any inspection station. Inspection has to be done annually, so that's a little more of a pain than some states which don't require trailers to be inspected every year, but the initial registration process is trivial.
MA is a pain with most of their laws; it's hard for me to believe that this area was the birthplace of this nation's freedom but that is another tirade for another time.
MA does have a provision for homemade trailers but there are a lot of gaps in how to go about it and have heard different variations of what I'm supposed to do. I find very little official info on the MA RMV website and calling is typically a useless exercise. What I find on the web says that you need proof of insurance and your receipts for materials. You call your insurance company and they set up a policy. Then you take the trailer to the local office with your paperwork, they inspect it, assign a VIN number and you are on your way......supposedly. But I've also read that insurance companies can deny coverage for something homemade. I haven't called mine yet but found a couple comments on snowmobile forums that this was a problem. There is also the small detail of anything on a MA road needs to have insurance and a
permanent tag. If it doesn't, it can be impounded on the spot. MA doesn't even recognize temporary tags from other states! I've read that pleading with the cop that you are on your way to the RMV and producing all of the documentation doesn't always work. So I'm not sure how someone gets a homemade trailer to the RMV legally other than loading it onto another trailer.......but if I had a trailer, I wouldn't need to build my own trailer.
I suppose I could rent a Uhaul trailer to get it down there but that is more time, expense and hassle. You have even bigger issues if you buy a used trailer that is missing its VIN and statement of origin paperwork.
So I'm mostly on a fact finding mission this winter. I'm not ruling out homemade yet but using a "kit" trailer gets me around most of the large hassles.