Most listings are in the $10's per square foot per year. The Dover region is seeing a decline in rates. In the last 3 months, the median rate decreased $1 per sqft per year. That's a 4% decline in rent.
Compared to the rest of the Greater Boston market, the Dover submarket has lower rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 11 listings have been posted online, which means spaces most likley are going fast. 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 560 sqft. Most buildings in this region are around 2 floors. Most buildings in this market were built in 1900 and are Class Class B.