On average, listings lease in the $50's per square foot per year. The Silicon Valley region is going through a an increase in rates. In the last 3 months, the median rate increased $4 per sqft per year. That's a 8% rise in rent.
In the last 90 days, 819 listings have been posted online, so you'll want to check back regularly for new listings. About 14% of the available leases 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 on the market, so finding a space for a small business might be tough.
Even though the median size is 3,100 sqft, there are still 0 listings below 2,000 sqft. Most properties in this area are close to 2 floors. Most buildings in this market were built in 1982 and are Class B.