On average, listings lease in the $20's per square foot per year. The Fort Washington submarket is experiencing a a boost in rates. In the last 3 months, the median rate increased $21 per sqft per year.
Compared to the rest of the Washington D.C. market, the Fort Washington region has less expensive rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 2 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 on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,120 sqft.