Most listings are in the $0's per square foot per year. The Castro Valley region is going through a decrease in rates. In the last 3 months, the median rate fell $32 per sqft per year. That's a 100% decline in rent.
In the last 90 days, 0 listings have been made available, which means leases most likley are going fast. You'll want to be prepared to make an offer immediately. About NaN% of the available space in the Castro Valley 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 on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,110 sqft. Most buildings in this market are approximately 1 stories. Most buildings in this market were built in 1982.