Addendum for guest staying 30 days?

[Richie Valadez]

My tenant is planning to be out of the country for a month and has asked if a friend can stay during that period to house sit.   I don't have a problem with this if the guest completes a background check.   The length of the stay is greater than what is allowed in the lease.   Should I have the tenant and guest sign an addendum stating the guest will follow all rules and terms of lease and leave by a certain date?