On average, listings lease in the $20's per square foot per year. The Ashburn submarket is seeing a an increase in rates. In the last 3 months, the median rate increased $1 per sqft per year. That's a 5% increase in rent.
Compared to the rest of the Washington D.C. market, the Ashburn submarket has lower rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 8 listings have been made available, which means office spaces are probably going fast. You'll want to be prepared to tour spaces as quick as possible. About 75% of the available space in the Ashburn are subleases, so you might be able to snag a great spot on a short term. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,600 sqft. Most buildings in this market are close to 2 stories. Most buildings in this area were built in 2002 and are Class A.