Tenants in social housing are stuck. Often they can only move by exchanging homes. A senior who lives too large and wants a smaller house, for example because the children have left home, can then exchange with a young family that is looking for a place. This is legally allowed, sometimes even with retention of rent. And socially, this helps people find a more suitable home, who would otherwise have stayed in their old house. Tenants who want to exchange each other's front door keys only encounter all kinds of obstacles. For example, corporations regularly turn against an exchange. Why? Money often turns out to be a reason.