Accurate measurements of profit

Yeah, well it is a given that capital gains will be taxed.  However, I think it is important to consider the reduction in income tax offered by negative gearing, if you choose to negative gear.  Depending upon your total taxable income and the amount of your tax loss, it could be a significant saving in tax and it is appropriate to consider that when deciding how your investment is performing. If your taxable income is reasonably static, then it is fairly easy to predict, however, if like me, you work for yourself and your taxable income could be $200K one year and a loss the next, then it is certainly difficult to obtain comparable information.

Personally, I'd rather just make money than lose it to save tax.

One important tax concept is the idea of Pay as you go withholding instalments.  This is the system where the ATO taxes a business in instalments  in the current year based on the previous years taxable income.  In the first year that it happens to a business, it can see the business being required to meet two years worth of income tax in the one year as the business moves from being taxed in arrears to being taxed an estimated amount in advance, to be reconciled when the businesses income tax return is lodged (much like it works for an employee).  If you do strucuture yourself as a business, and you do make a profit, then you can expect the ATO to ask you to pay PAYG Instalment tax the following tax year.  This can be quite hard on the cash flow, so it is worth being aware of and planning for.

S

I prefer a spreadsheet, because you can, in advance, do things like change the interest rate and see if you are still going to make money, or drop the sell value, etc etc.  In the planning stage, I'm thinking of all the things that could go wrong, how likely they are, and I have several different columns for different scenarios, eg, what I expect to happen, and the worse case scenario, and a likely combination of events etc etc.