Partitioning expenses across multiple units

[Robert James]

I own a duplex, live in one unit.

It has two separate street addresses, but the mortgage interest, etc. is apportioned in a lump sum to the whole building.

When it comes to apportioning expenses such as mortgage interest, should I split it 50:50, or, for example, proportionally based on the number of bedrooms in each unit (one unit has 2 bedrooms, one has 4, so it would be a 33:66 split)

[Terry Miller]

One thing I learned while doing my MBA was that many business situations don't have any hard-and-fast rules, and you simply do something that makes sense. Later, you may come to find that there are some specific laws/regulations/standard procedures, and then you would adjust accordingly.

@Robert James:

While I can see your logic in thinking 50:50, because it is two units, I can also see your logic in 33:67. I would go further on that line of thinking, though, and look at it in a breakdown based on square footage.