On average, listings lease in the $20's per square foot per year. The National City region is going through a a rise in rates. In the last 3 months, the median rate increased $10 per sqft per year. That's a 67% increase in rent.
Compared to the rest of the San Diego market, the National City submarket has smaller rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 4 listings have been posted online, which means new availabilities might be 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.
Even though the median size is 12,470 sqft, there are still 0 office spaces below 2,000 sqft. Most properties in this region are around 1 floors. Most buildings in this market were built in 1974 and are Class B.