That’s an implementation detail, but I would say: two-bedroom apartment or small detached house in decent condition (no bugs, rot, mold, etc, water and electrical working, not in the middle of a crime hotspot or environmental disaster, reasonable access to shops and services, no oddball problems like being on the approach path for a major airport) for no more than a third of the employee’s after-tax salary. A place where it wouldn’t be torture for the average person to live, with maybe one or two other people if it suits them.