Most listings are in the $0's per square foot per year. The Mission region is going through a decline 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, 1 listings have been listed, which means leases most likley are leasing quickly. You'll want to be prepared to make an offer immediately. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around sqft. Most properties in this region are close to 1 floors. Most buildings in this region were built in 2006 and are Class A.