Most listings are in the $10's per square foot per year. The Kent County submarket is going through a an increase in rates. In the last 3 months, the median rate increased $16 per sqft per year.
In the last 90 days, 0 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. About NaN% of the available leases in the Kent County are subleases, so you will probably need to consider the implications of signing a direct lease with the building. 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 2,100 sqft. Most buildings in this region were built in 1951.