On average, listings lease in the $10's per square foot per year. The Brentwood submarket is experiencing a decrease in rates. In the last 3 months, the median rate decreased $13 per sqft per year. That's a 46% decline in rent.
Compared to the rest of the East Bay market, the Brentwood region has lower rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 5 listings have been listed, which means listings most likley are going fast. You'll want to be prepared to make an offer immediately. About 40% of the available leases in the Brentwood are subleases, so you might be able to snag a great spot on a short term. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,460 sqft. Most buildings in this area are around 1 floors. Most buildings in this market were built in 2003 and are Class A.