Renting out part of your garage

[Bruce P.]

Hi,

Living in the state of CA (Malibu / Ventura County area), how can one safely and legally rent out part of their garage to an existing tenant? (It's a house hack situation - owner lives on-site and rents out rooms to roommates/tenants). One of the tenants wants to store their motorcycle there (rather than on the street).  Does the owner just amend the existing room lease agreement? I saw threads talking about renting out the whole garage as a self-storage unit but not just letting someone keep some of their stuff in there for a fee. Asking for a friend. Thanks!