On average, listings lease in the $40's per square foot per year. The McLean region is going through a an increase in rates. In the last 3 months, the median rate increased $7 per sqft per year. That's a 22% increase in rent.
Compared to the rest of the Washington D.C. market, the McLean submarket has higher rates, and you'll have to negotiate above asking rent to be in this hot region.
In the last 90 days, 10 listings have been made available, which means new listings might be 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 960 sqft. Most buildings in this market are approximately 5 stories. Most buildings in this market were built in 1980 and are Class A.