Tanya,
From my experiences you really just need to do the maths of expenses (paper and real) vs income.
For example, income will = rent
Expenses = interest on loan, property management fees, rates, insurance, maintenance (factor in although hard to predict sometimes).
Then recognise that there will be paper losses attached to your property in the way of depreciation on building and fittings.

If your income is greater than your expenses then you are cash flow positive.