The typical asking rate per listing is in the $20's per square foot per year. The Manassas submarket is going through a decrease in rates. In the last 3 months, the median rate fell $2 per sqft per year. That's a 8% decline in rent.
Compared to the rest of the Washington D.C. market, the Manassas region has less expensive rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 28 listings have come on the market, which means listings are probably going fast. You'll want to be prepared to make an offer immediately. About 4% of the office spaces in the Manassas are subleases, so you will probably have to consider a longer term lease. 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 2,080 sqft. Most properties in this market are approximately 2 stories. Most buildings in this region were built in 1988 and are Class B.