Home-sharing (renting a room to, or from, another older adult) and co-housing communities are increasingly common solutions built specifically around mutual support among unrelated residents.
Home-sharing
Organizations exist specifically to match older adults for home-sharing, often with a vetting process similar to a roommate service, addressing both companionship and shared expenses.
Co-housing
Intentional communities with private units and shared common spaces, designed to encourage daily interaction while preserving independence — a middle ground between fully independent living and a shared household.
Search "home sharing program" plus your area, or "senior cohousing" nationally — several established networks operate across the U.S.