On average, listings lease in the $20's per square foot per year. The Londonderry submarket is going through a a boost in rates. In the last 3 months, the median rate rose $1 per sqft per year. That's a 6% rise in rent.
Compared to the rest of the Greater Boston market, the Londonderry region has smaller rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 28 listings have been posted online, which means office spaces 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 posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,550 sqft. Most buildings in this region are approximately 2 stories. Most buildings in this area were built in 1988 and are Class B.