On average, listings lease in the $20's per square foot per year. The Mission region is going through a a rise in rates. In the last 3 months, the median rate went up $9 per sqft per year. That's a 47% increase in rent.
In the last 90 days, 30 listings have been made available, which means new listings are probably going fast. You'll want to be prepared to make an offer immediately. About 13% of the listings in the Mission 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 on the market, so finding a space for a small business might be tough.
Even though the median size is 6,420 sqft, there are still 0 listings below 2,000 sqft. Most properties in this area are around 2 floors. Most buildings in this area were built in 1969 and are Class B.