In the last 90 days, 1 listings have come on the market, which means office spaces most likley are leasing quickly. You'll want to be prepared to make an offer immediately. About 900% of the available leases in the Brownsville 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.
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 1990 and are Class A.