The typical asking rate per listing is in the $20's per square foot per year. The Brentwood region is seeing a a rise in rates. In the last 3 months, the median rate increased $22 per sqft per year. That's a Inf% rise in rent.
Compared to the rest of the East Bay market, the Brentwood submarket has less expensive rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 20 listings have been made available, which means new availabilities are probably leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 5% of the available leases in the Brentwood are subleases, so you will probably need to sign a longer term lease with the landlord directly. 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 1,940 sqft. Most properties in this region are approximately 1 stories. Most buildings in this area were built in 2003 and are Class A.