The typical asking rate per listing is in the $20's per square foot per year. The Bull Run region is going through a decrease in rates. In the last 3 months, the median rate decreased $1 per sqft per year. That's a 2% decrease in rent.
Compared to the rest of the Washington D.C. market, the Bull Run region has smaller rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 37 listings have been posted online, which means spaces most likley are leasing quickly. You'll want to be prepared to make an offer immediately. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,130 sqft. Most buildings in this area are around 2 stories. Most buildings in this area were built in 1988 and are Class B.