[baseonmars]

In my experience it just mean they're sharing the property, not living in the same room.

[chrisseaton]

Ah. We say housemates to mean that, and roommates to mean if you are actually sharing a room (which wouldn't be likely).

[taurath]

Yeah - people don't tend to say "house" when they mean "apartment" here, so a housemate would imply that you are living in a house.