In the last 90 days, 4 listings have been posted online, which means office spaces most likley are leasing quickly. You'll want to be prepared to make an offer immediately. About 25% of the available space in the Wilmington 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 on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,000 sqft. Most buildings in this region were built in 2006.