Create a model to Negative Gearing and Tax Credits AUS-US

Need a model built in excel spreadsheet that helps me understand how much negative gearing can help me save money: - Having a property rented in NSW with a home loan (considering a 5/6% interest rate in AUS) - Owners living in the US (not considered AUS citizens for tax purposes) - Considering the tax credits for US and AUS income tax - Considering a withdraw of the home loan account for investment in the US (with a 4% interest in the US) How much money makes sense to withdraw from the home loan in Australia for negative gearing and tax credits considering the money is needed in the US to buy another property. Happy to clarify any questions - I believe such model already exist somewhere...