On average, listings lease in the $20's per square foot per year. The Mantua region is seeing a a rise in rates. In the last 3 months, the median rate rose $29 per sqft per year.
Compared to the rest of the Washington D.C. market, the Mantua region has smaller rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 0 listings have come on the market, which means office spaces are probably going fast. You'll want to be prepared to make an offer immediately. About Inf% of the available space in the Mantua are subleases, so you might be able to sign a shorter term by taking over a previous lease. 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 1,130 sqft.