Most listings are in the $40's per square foot per year. The Miami-Dade County region is going through a a boost in rates. In the last 3 months, the median rate rose $45 per sqft per year.
In the last 90 days, 362 listings have been made available, so you'll want to check back regularly for new listings. About 164% of the listings in the Miami-Dade County are subleases, so you might be able to find a shorter term or below market rent. 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 2,160 sqft. Most properties in this region are close to 3 stories. Most buildings in this area were built in 1982 and are Class A.