HELOC Interest: Which Property to Apply as Expense?

[Evan Williams]

I am in the process of buying a rental property, and have taken out a HELOC on one of my existing rentals to use as the down payment for another. In this scenario, against which property should the HELOC interest expense be applied when calculating cash flow? The first property (on which the HELOC was taken), or the second (for which HELOC funds were used as a down payment)?