On average, listings lease in the $50's per square foot per year. The Silicon Valley region is going through a a rise in rates. In the last 3 months, the median rate rose $53 per sqft per year.
In the last 90 days, 819 listings have come on the market, so you'll want to check back regularly for new listings. About 89% of the office spaces in the Silicon Valley 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.
Even though the median size is 3,360 sqft, there are still 0 office spaces below 2,000 sqft. Most buildings in this area are around 2 floors. Most buildings in this region were built in 1982 and are Class B.