Most listings are in the $10's per square foot per year. The Delaware region is seeing a an increase in rates. In the last 3 months, the median rate increased $15 per sqft per year.
In the last 90 days, 2 listings have been posted online, which means new availabilities might be going fast. You'll want to be prepared to make an offer immediately. About 50% of the available leases in the Delaware are subleases, so you might be able to sign a shorter term by taking over a previous lease. 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 1,390 sqft. Most buildings in this area are around 2 stories. Most buildings in this area were built in 1946 and are Class C.