The typical asking rate per listing is in the $10's per square foot per year. The South Portland submarket is going through a an increase in rates. In the last 3 months, the median rate went up $1 per sqft per year. That's a 7% rise in rent.
In the last 90 days, 20 listings have come on the market, which means spaces are probably leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 5% of the available space in the South Portland are subleases, so you will probably need to sign a longer term lease with the landlord directly. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
Even though the median size is 2,730 sqft, there are still 0 spaces below 2,000 sqft. Most buildings in this area are approximately 2 floors. Most buildings in this area were built in 1974 and are Class A.