Most listings are in the $20's per square foot per year. The Casa Grande submarket is going through a decline in rates. In the last 3 months, the median rate decreased $13 per sqft per year. That's a 37% decline in rent.
Compared to the rest of the Phoenix Metropolitan Area market, the Casa Grande region has less expensive rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 3 listings have been listed, which means leases most likley are going fast. You'll want to be prepared to make an offer immediately. 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 2,330 sqft. Most properties in this market are around 1 floors. Most buildings in this area were built in 2003 and are Class B.