On average, listings lease in the $0's per square foot per year. The Reston region is seeing a decrease in rates. In the last 3 months, the median rate decreased $35 per sqft per year. That's a 100% decline in rent.
In the last 90 days, 33 listings have been made available, which means new availabilities most likley are going fast. 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 sqft. Most buildings in this market are approximately 5 floors. Most buildings in this area were built in 1987 and are Class A.