In the last 90 days, 2 listings have been listed, which means new availabilities most likley are leasing quickly. You'll want to be prepared to make an offer immediately. About 50% of the available leases in the Downey 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 2 stories. Most buildings in this area were built in 1968 and are Class B.