Most listings are in the $20's per square foot per year. The Greater Austin region is going through a a boost in rates. In the last 3 months, the median rate went up $1 per sqft per year. That's a 2% rise in rent.
In the last 90 days, 1138 listings have come on the market, so you'll want to check back regularly for new listings. About 8% of the listings in the Greater Austin 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 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 2,400 sqft. Most properties in this area are around 2 stories. Most buildings in this market were built in 1986 and are Class A.