We are currently buying a house in Caboolture. I know because only one of us is working (me) our borrowing power is about 220k, but we have a 170k deposit so we are bidding on a 340k house, giving us an eventual mortgage of 160k. Your borrowing power is the maximum amount of money you can owe at the end of the day and have to start repaying... it doesn't matter what the deposit is.

HTH
M