The typical asking rate per listing is in the $20's per square foot per year. The Portsmouth County submarket is going through a an increase in rates. In the last 3 months, the median rate rose $5 per sqft per year. That's a 31% rise in rent.
In the last 90 days, 26 listings have been listed, which means listings are probably leasing quickly. You'll want to be prepared to make an offer immediately. 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 2,310 sqft. Most properties in this market are close to 2 floors. Most buildings in this area were built in 1978 and are Class C.