The typical asking rate per listing is in the $10's per square foot per year. The Oakland region is experiencing a a boost in rates. In the last 3 months, the median rate went up $18 per sqft per year.
In the last 90 days, 1 listings have been listed, which means spaces are probably going fast. You'll want to be prepared to make an offer immediately. About 100% of the listings in the Oakland 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 available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,110 sqft. Most buildings in this region are around 2 floors. Most buildings in this region were built in 1989 and are Class B.