New BARRRR Article Question

[Daniel Y.]

The recent article regarding BARRRR is very interesting written by Brandon Hall. One question I had in mind if anyone could answer is what would be considered as "In-service" for 2-4 units. If I had a duplex and one unit was occupied, and I was fixing up the other vacant unit. Would the whole property be considered as "In service" so I could write off most of the updates in the vacant unit as "operational cost" instead of depreciating it? Or would the IRS try to separate it, saying that the vacant unit was not advertised, and therefore is not in service?