Most listings are in the $0's per square foot per year. The Oakland submarket is going through a decrease in rates. In the last 3 months, the median rate decreased $16 per sqft per year. That's a 100% decrease in rent.
In the last 90 days, 0 listings have come on the market, which means spaces most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About NaN% of the available space in the Oakland are subleases, so you will probably have to focus your search on direct office leases. 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 sqft. Most buildings in this region were built in 2004 and are Class C.