On average, listings lease in the $10's per square foot per year. The Willimantic submarket is seeing a a rise in rates. In the last 3 months, the median rate rose $16 per sqft per year.
Compared to the rest of the Greater Boston market, the Willimantic region has smaller rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 2 listings have come on the market, which means listings most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. About 50% of the available leases in the Willimantic are subleases, so you might be able to find a shorter term or below market rent. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 850 sqft. Most buildings in this market are around 2 floors. Most buildings in this area were built in 1925 and are Class C.