Most listings are in the $10's per square foot per year. The New Castle submarket is seeing a a boost in rates. In the last 3 months, the median rate rose $15 per sqft per year.
In the last 90 days, 0 listings have been posted online, which means leases might be going fast. You'll want to be prepared to make an offer immediately. About NaN% of the listings in the New Castle are subleases, so you will probably need to sign a longer term lease with the landlord directly. 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 1,160 sqft. Most buildings in this area were built in 1900 and are Class A.