The typical asking rate per listing is in the $10's per square foot per year. The Imperial Beach submarket is seeing a a rise in rates. In the last 3 months, the median rate went up $2 per sqft per year. That's a 9% increase in rent.
Compared to the rest of the San Diego market, the Imperial Beach 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 new availabilities might be leasing quickly. 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 1,100 sqft. Most buildings in this area were built in 1975 and are Class C.