Casitas are common home amenities in AZ and was a top priority for us when we right-sized as we moved when our son was a HS senior and we wanted him to have his own private space when he came home from school as well as have a guest house for visitors. When our son moved out, I completely redecorated the casita (as I posted here) and use it as my “she-shed” when it’s not occupied by visitors. It has a full bath, bedroom, walk-in closet, sitting room, and kitchenette. It’s definitely rentable, too, though we put that off due to the pandemic. Rentals are restricted in our community to friends and family (overflow guests) of current members and for no more than one month per occupancy. Several of our friends rent theirs and no one has had an issue, so we will revisit that option.
What I especially like about this extra space is that it’s there when we need it but doesn’t require any upkeep when we don’t and, because it’s not part of the main house, it doesn’t feel like wasted daily space.