On average, listings lease in the $10's per square foot per year. The Brentwood submarket is experiencing a an increase in rates. In the last 3 months, the median rate rose $18 per sqft per year.
In the last 90 days, 4 listings have been made available, which means office spaces might be leasing quickly. You'll want to be prepared to make an offer immediately. About 25% of the available space in the Brentwood are subleases, so you might be able to find a shorter term or below market rent. 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 2,200 sqft. Most buildings in this market were built in 1970 and are Class C.