On average, listings lease in the $30's per square foot per year. The Oceanside submarket is going through a a rise in rates. In the last 3 months, the median rate increased $32 per sqft per year.
Compared to the rest of the San Diego market, the Oceanside submarket has less expensive rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 64 listings have come on the market, so you'll want to check back regularly for new listings. About 47% of the available leases in the Oceanside are subleases, so you might be able to sign a shorter term by taking over a previous lease. 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 1,420 sqft. Most buildings in this market are around 2 floors. Most buildings in this market were built in 1987 and are Class B.