On average, listings lease in the $10's per square foot per year. The Manassas Park submarket is seeing a an increase in rates. In the last 3 months, the median rate went up $20 per sqft per year.
Compared to the rest of the Washington D.C. market, the Manassas Park region has smaller rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 4 listings have come on the market, which means new listings are probably leasing quickly. 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 1,000 sqft. Most buildings in this area were built in 1946.