Most listings are in the $20's per square foot per year. The Arlington region is seeing a a rise in rates. In the last 3 months, the median rate increased $1 per sqft per year. That's a 5% increase in rent.
Compared to the rest of the DFW Metroplex market, the Arlington region has less expensive rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 126 listings have been posted online, so you'll want to check back regularly for new listings. About 2% of the listings in the Arlington are subleases, so you will probably need to consider the implications of signing a direct lease with the building. 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 1,840 sqft. Most buildings in this area are around 2 floors. Most buildings in this area were built in 1985 and are Class B.