On average, listings lease in the $20's per square foot per year. The Oceanside region is seeing a a boost in rates. In the last 3 months, the median rate rose $4 per sqft per year. That's a 16% rise in rent.
Compared to the rest of the San Diego market, the Oceanside region has lower rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 14 listings have been made available, which means leases are probably going fast. You'll want to be prepared to tour spaces as quick as possible. About 7% of the listings in the Oceanside are subleases, so you will probably need to consider the implications of signing a direct lease with the building. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,680 sqft. Most properties in this region are close to 2 floors. Most buildings in this market were built in 1984 and are Class B.