Thanks for your advice:

In terms of PPOR, I believe it would be, we have both lived in it for 6 Months and my partner recieved the FHOG.  I though if I were to buy one that the new one would become PPOR and we can turn the existing one into the investment property and maybe extend the loan and make it cash flow positive so it can look after itself – or does this take time ?
So I am gathering it would be better to build equity on existing one and borrow 100% against equity for a tax saving on the interest being paid on the next one we buy.