My wife and I have very different feeling about yard sales.
She absolutely loves them. If she's got cash in her pocket, we cannot pass a yard sale without stopping. She's a sucker for a good deal, and God lover her, she always finds one. It's a like a rabbit she can pull our of her hat whenever she wants. Personally, I'm no fan of yard sales. I'm a man of very material wants, kinda hate crowds, and openly hate the way people are in heavy traffic areas during yard sales.
That said, in the 20+ years my wife and I have been together, we've only had two yard sales. Both did just fine and we made a little cash, but on thing that never occurred to me was that I had to check in with anyone about having one. I always just assumed you threw your junk in the front yard and haggled with the neighbors over price.
Several Maine towns require you to have a permit.
In fact, most towns right here in the Bangor area require a permit to have a yard sale. It likely falls under the category of doing business out of your home. Because you know, God forbid you make any money that your town or the state of Maine doesn't get a cut of. But if you're having a yard sale in Bangor, Brewer, or even Veazie, You'll need a permit to have your sale. They're usually pretty easy to grab online.
Some towns either don't have the requirement for a permit at all, or there doesn't seem to be any verbiage within their town ordinances that imply you need one. Folks living in Hampden, Orono, and Old Town don't seem to have much to worry about.
Some towns, in addition to requiring a permit to have a yard sale, might have laws about how many yard sales you can have in a year. Some allow just one, some have up to three. On the other hand, let's be real. I've never seen anyone out at yard sales asking for permits. I'm not 100% sure what the punishment is for such an egregious and flagrant disregard for the law, but I bet it won't keep you up at night. So, you be you. I won't tell.