In the last 90 days, 1 listings have come on the market, which means listings most likley are going fast. You'll want to be prepared to make an offer immediately. About 600% of the available leases 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 available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around sqft. Most buildings in this market are around 1 floors. Most buildings in this area were built in 2006 and are Class A.