Ultra low rates are at some point going to attract investors and owner occupiers to borrow more. The RBA are likely putting some fear into the market to minimise this.
Of course you have to pay back the principal... But at 0% it is free money. You get to take it, invest it, create income from it and it costs you nothing. 2% may not be free but it is bloody close to it. When you consider Sydney rental yield is 3-4% it becomes an attractive proposition.
Especially if you are only putting 10% down and generating yield on the full purchase price.
