On average, listings lease in the $10's per square foot per year. The Willimantic region is going through a a boost in rates. In the last 3 months, the median rate went up $16 per sqft per year.
Compared to the rest of the Greater Boston market, the Willimantic region has less expensive rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 2 listings have been made available, which means new availabilities are probably leasing quickly. You'll want to be prepared to make an offer immediately. About 50% of the available space in the Willimantic are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet available, 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 region are approximately 2 stories. Most buildings in this region were built in 1925 and are Class C.