The typical asking rate per listing is in the $10's per square foot per year. The Irmo region is experiencing a decline in rates. In the last 3 months, the median rate fell $4 per sqft per year. That's a 20% decline in rent.
In the last 90 days, 4 listings have been made available, which means new listings most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. 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 1,300 sqft. Most buildings in this area were built in 2007 and are Class B.