In the last 90 days, 6 listings have been posted online, which means leases most likley are going fast. You'll want to be prepared to make an offer immediately. About 50% of the available leases in the Horsham are subleases, so you might be able to find a shorter term or below market rent. 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 sqft. Most properties in this area are around 2 floors. Most buildings in this region were built in 1987 and are Class B.