Most listings are in the $20's per square foot per year. The Harrisburg region is experiencing a a rise in rates. In the last 3 months, the median rate rose $5 per sqft per year. That's a 28% rise in rent.
In the last 90 days, 31 listings have been made available, which means new listings most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 3% of the available leases in the Harrisburg 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 posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,750 sqft. Most buildings in this market are around 3 floors. Most buildings in this region were built in 1936 and are Class B.