A couple moving into a house share

Two people sharing one bedroom is two people using the kitchen, the bathroom, the hot water and the internet, and one room's worth of rent. Almost every house share that has done this lands in the same place: the room pays a room's share of the rent, and the couple pays two people's share of everything that scales with bodies. Where it goes wrong is when nobody says that out loud first.

Rent by room, bills by person

It sounds like a compromise and it is closer to a principle. Rent buys floor space, and the couple has taken one room off the market whatever their number. Utilities buy consumption, and there are demonstrably more people consuming.

Splitting the whole thing by head charges the couple twice for the same room; splitting it all by room hands them a discount the others are paying for. The two-part version is the one both sides can look at without flinching.

The part nobody raises: voting

A four-person house where two of the people arrive together is not a four-way decision any more. On the thermostat, on a guest policy, on whether to renew, the couple is one bloc and everybody knows it before anybody says it.

Naming that in advance is oddly disarming. It is much easier as a joke in week one than as an accusation in month eight, and households that acknowledge it tend to defer more deliberately when it matters.

And what happens if they split up

Uncomfortable, and worth ten seconds. If one of them leaves, is the room still let at a couple's rate, does the remaining person cover it alone, or does the household look for somebody new? Any answer is fine. Not having one means the question gets decided during a break-up.