advise on paying out mortgage

Wanted to get some general advice on a situation I may be entering into. Currently I have a mortgage with a bank. My old man is thinking of paying out the loan for me and I repay him back at a more favorable rate than the bank, obviously without the fees and the such. The way it will be structured is I will get the title to the house, and it will be a good will loan, i.e. I pay him back in good faith at an agreed monthly repayment, with no contractual agreement. I like the idea, and it would save me tonnes on my mortgage.

What I wanted to know is does this affect me with regards to tax? Technically it is a lump sum payment to me (or the bank in this case) of a significant amount of money to pay off the loan. Do I have to pay tax on this money and does the ATO look at such a payment in a negative way, and is there anything that I need to keep in mind if I enter into this deal? Can anyone see any problems with such an arrangement that I should be careful of.

Cheers for any advice.

Greg