Most listings are in the $20's per square foot per year. The Dunedin submarket is going through a a boost in rates. In the last 3 months, the median rate increased $2 per sqft per year. That's a 11% increase in rent.
In the last 90 days, 5 listings have been made available, which means leases most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. About 20% of the available leases in the Dunedin 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 posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,000 sqft. Most buildings in this area are close to 2 stories. Most buildings in this region were built in 1979 and are Class A.