The typical asking rate per listing is in the $30's per square foot per year. The McLean region is going through a decrease in rates. In the last 3 months, the median rate fell $6 per sqft per year. That's a 15% decline in rent.
Compared to the rest of the Washington D.C. market, the McLean region has higher rates, and you'll have to negotiate above asking rent to be in this hot submarket.
In the last 90 days, 12 listings have been listed, which means spaces most likley are leasing quickly. You'll want to be prepared to make an offer immediately. 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 1,200 sqft. Most properties in this area are approximately 5 stories. Most buildings in this region were built in 1980 and are Class A.