Most listings are in the $20's per square foot per year. The New Hampshire region 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 3% rise in rent.
In the last 90 days, 1500 listings have come on the market, so you'll want to check back regularly for new listings. About 1% of the listings in the New Hampshire are subleases, so you will probably need to sign a longer term lease with the landlord directly. 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 1,870 sqft. Most properties in this market are approximately 2 stories. Most buildings in this region were built in 1950 and are Class Class B.