Compared to the rest of the Washington D.C. market, the Manassas Park submarket has smaller rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 12 listings have been made available, which means new listings are probably leasing quickly. 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.