On average, listings lease in the $20's per square foot per year. The Manassas region is seeing a an increase in rates. In the last 3 months, the median rate went up $24 per sqft per year.
Compared to the rest of the Washington D.C. market, the Manassas submarket has lower rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 29 listings have been made available, which means leases are probably leasing quickly. You'll want to be prepared to make an offer immediately. About 107% of the available space in the Manassas are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
Even though the median size is 2,950 sqft, there are still 0 leases below 2,000 sqft. Most properties in this area are around 2 floors. Most buildings in this area were built in 1989 and are Class B.