Most listings are in the $10's per square foot per year. The Rincon region is experiencing a an increase in rates. In the last 3 months, the median rate went up $19 per sqft per year.
In the last 90 days, 0 listings have been listed, which means spaces might be leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About Inf% of the available leases in the Rincon are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 930 sqft. Most buildings in this area were built in 2007 and are Class B.