California Code, Evidence Code - EVID § 817

(a) Subject to subdivision (b), when relevant to the determination of the value of property, a witness may take into account as a basis for an opinion the rent reserved and other terms and circumstances of any lease which included the property or property interest being valued or any part thereof which was in effect within a reasonable time before or after the date of valuation, except that in an eminent domain proceeding where the lease includes only the property or property interest being taken or a part thereof, such lease may not be taken into account in the determination of the value of property if it is entered into after the filing of the lis pendens.

(b) A witness may take into account a lease providing for a rental fixed by a percentage or other measurable portion of gross sales or gross income from a business conducted on the leased property only for the purpose of arriving at an opinion as to the reasonable net rental value attributable to the property or property interest being valued as provided in Section 819 or determining the value of a leasehold interest.