On average, listings lease in the $10's per square foot per year. The Westerly region is experiencing a a rise in rates. In the last 3 months, the median rate rose $14 per sqft per year. That's a Inf% increase in rent.
Compared to the rest of the Greater Boston market, the Westerly submarket has lower rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 1 listings have been made available, which means new availabilities most likley are leasing quickly. You'll want to be prepared to make an offer immediately. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,000 sqft. Most buildings in this area are approximately 2 floors. Most buildings in this area were built in 1950 and are Class A.