Compared to the rest of the Washington D.C. market, the Manassas Park region has lower rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 12 listings have been made available, which means spaces are probably going fast. You'll want to be prepared to make an offer immediately. 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 1,550 sqft. Most buildings in this area were built in 1983 and are Class A.