On average, listings lease in the $20's per square foot per year. The New Castle County submarket is going through a an increase in rates. In the last 3 months, the median rate increased $1 per sqft per year. That's a 6% rise in rent.
In the last 90 days, 193 listings have come on the market, so you'll want to check back regularly for new listings. About 1% of the available leases in the New Castle County are subleases, so you will probably have to focus your search on direct office leases. 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 2,290 sqft. Most properties in this market are around 2 stories. Most buildings in this region were built in 1985 and are Class A.