Most listings are in the $30's per square foot per year. The Manassas Park County submarket is going through a a rise in rates. In the last 3 months, the median rate increased $16 per sqft per year. That's a 79% increase in rent.
In the last 90 days, 16 listings have been posted online, which means leases are probably going fast. You'll want to be prepared to tour spaces as quick as possible. 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 460 sqft. Most buildings in this region were built in 1983 and are Class B.