Legal Question in Landlord & Tenant Law in California

An odd old feature of English common law of property from the middle ages, has carried over into modern times. Back when property was owned in large estates by feudal lords and farmed by peasants, with lots of woods and fields to hunt in, co-owners of property could share in the use of the property at the same time without bumping into each other, figuratively or literally. As a result, the law held that each owner had the full rights of ownership as if they each individually owned it. As you can imagine, that makes for problems in modern times with modern properties being as small as a studio condo, but that is still the law. So the answer to your question is, either or each of them can rent it out, and in fact they could legally each rent it out to different people. This is why it is essential that when more than one person owns property, unless they are currently married, they must have a co-ownership agreement to govern how the property will be used and managed. Otherwise sooner or later, when, not if, there is going to be conflict and problems.