On average, listings lease in the $20's per square foot per year. The Santee region is going through a an increase in rates. In the last 3 months, the median rate increased $21 per sqft per year.
Compared to the rest of the San Diego market, the Santee submarket has less expensive rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 4 listings have been listed, which means spaces 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 posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,390 sqft. Most buildings in this region are close to 2 stories. Most buildings in this area were built in 1972 and are Class C.