On average, listings lease in the $20's per square foot per year. The Falls Church region is experiencing a a rise in rates. In the last 3 months, the median rate went up $26 per sqft per year.
Compared to the rest of the Washington D.C. market, the Falls Church region has lower rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 1 listings have been posted online, which means spaces most likley are going fast. You'll want to be prepared to make an offer immediately. About 900% of the listings in the Falls Church 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 posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 800 sqft. Most properties in this region are close to 2 stories. Most buildings in this region were built in 1980 and are Class B.