The typical asking rate per listing is 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 $3 per sqft per year. That's a 7% rise in rent.
In the last 90 days, 841 listings have come on the market, so you'll want to check back regularly for new listings. About 17% of the office spaces in the Silicon Valley are subleases, so you might be able to snag a great spot on a short term. 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 2,930 sqft, there are still 0 listings below 2,000 sqft. Most buildings in this region are around 2 floors. Most buildings in this market were built in 1983 and are Class A.