Legal Question in Landlord & Tenant Law in California

Sure, why not? The landlord can rent to whomever he wants and there is no requirement that they already live there.

It is very common in urban areas where many tenants may not have cars and many commuters may need parking. The U.C. Berkeley campus area is a prime example. Parking and living space are almost always rented separately around there, although of course tenants are free to rent a parking space too, and frequently get priority.