Hello Lisa!
After scouring the City of Pismo Beach's painfully vague website, I've noted a few pieces of information which you may find to be helpful. Firstly, it's important to point out that Pismo Beach, like many other California towns, has imposed stricter regulations on STRs in recent times.
The city has drawn a distinction between three types of authorized 'Less Than 30-Day Rentals,' specifically a "Short Term Rental," a "Vacation Rental," and a "Homestay Rental."
Short Term Rental - This is the permit you would apply for when pursuing a non-owner-occupied STR in the R-1, R-2, R-3, RSL, RSM, PR, OS-1 and OS zones. Unfortunately, the city is currently not accepting any new 'Short Term Rental' permits, but they are accepting renewals for existing permits. That means that if you find a property that already has the proper permit, it could continue to be operated legally, if the permit is renewed. However, if the property does not already have the permit, you will not be able to apply for a new one at the moment. Here's a map showing where 'Short Term Rentals' are allowed: Short Term Rentals Allowed Map
Vacation Rental - This is the necessary permit for non-owner-occupied STRs in the C-1, RR, R-4, CD, CD-C, CD-M, and CD-V zones. Luckily for you, the city is currently accepting Vacation Rental Permit Requests. However, given that the permit is only applicable for the above zones, which basically only cover multifamily/commercial properties, it limits your options substantially. Here's a map showing where these rentals are allowed: Vacation Rentals Allowed Map
Homestay Rental - Lastly, there is the option of a "Homestay Rental," but these are unrealistic for most investors. The homestay is an owner-occupied STR in which you basically rent out a part of your home while you live in it. Although the city's website doesn't explicitly address it, I am pretty sure that this permit is the one that is most likely to be approved out of the three, and offers the most lenience in terms of zoning regulations.
Here's a helpful link with additional information: Pismo Beach STRs
I operate out of the Central Coast, so if you have any questions please don't hesitate to reach out!