On average, listings lease in the $20's per square foot per year. The Lorton region is going through a an increase in rates. In the last 3 months, the median rate went up $26 per sqft per year. That's a Inf% rise in rent.
Compared to the rest of the Washington D.C. market, the Lorton submarket has less expensive rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 1 listings have been made available, which means spaces most likley are 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 150 sqft. Most properties in this market are around 1 stories. Most buildings in this area were built in 1979 and are Class A.