The typical asking rate per listing is in the $20's per square foot per year. The Exton region is going through a a rise in rates. In the last 3 months, the median rate increased $10 per sqft per year. That's a 55% rise in rent.
In the last 90 days, 1 listings have been posted online, which means spaces might be going fast. You'll want to be prepared to make an offer immediately. About 200% of the available space in the Exton 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 500 sqft. Most properties in this area are approximately 2 floors. Most buildings in this market were built in 1980 and are Class B.