The typical asking rate per listing is in the $20's per square foot per year. The Lorton submarket is going through 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 Lorton region has smaller rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 5 listings have been listed, which means leases are probably going fast. 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 600 sqft. Most properties in this area are around 2 stories. Most buildings in this market were built in 1985 and are Class A.