In the last 90 days, 0 listings have been listed, which means new availabilities most likley are leasing quickly. You'll want to be prepared to make an offer immediately. About NaN% of the listings in the Annandale are subleases, so you will probably need to consider the implications of signing a direct lease with the building. 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 sqft. Most buildings in this market were built in 1999 and are Class A.