The rule of thumb used to be take your gross income and multiply by 3 for the house that you can COMFORTABLY afford to buy. Banks will lend you a lot more than that so as others have said, don't base it on what they will lend you.

Just use one of the bank's mortgage calculators to work out what your repayments would be. Without knowing the price of houses in your area, it's impossible to know whether $500 a week is a good estimate or not.