It shouldn't be hard to find an off-season rental in that area, unlike others, such as Boston and some of the college towns.
One site that might help is;
Welcome To cape-ann-rentals.com
Another site says it specializes in short-term rentals, but there quite a few hotels listed. I noticed a cute bungalow, however on the first page:
Vacation Rentals in Gloucester, Rockport, Essex, Manchester
I would subscribe to one of the local newspapers or visit their classified section online.The Boston Globe or my personal fave: The Wicked Local Northshore Sunday paper online:
News - Peabody, MA - North Shore Sunday
There was a site I used years ago for a summer rental, but I can't remember what it was. It was VERY comprehensive and had nice properties. I'll post it if I can find it.