In an earlier live letter, we were told house sharing would let us designate up to five people as tenants:

Quote Originally Posted by Letter from the Produce LIVE XXIV
We have been receiving many requests for a feature to share housing privileges with another member, especially from those who have been eternally bonded. Players will be able to share their housing privileges with not only their eternal bond partners, but up to 5 players of their choosing. It’s similar to sharing one house with roommates. We’ll first implement it in this manner, and we’ll look into whether we should increase the amount of players who can be assigned for this privileges as we check feedback.
I'd love if they could expand the feature from the 3 tenants we have now to the 5 tenants we were originally told would be allowed. My house is currently the hangout spot for a number of former FC members, and it would be great if I could give at least two more people access to it.