I think you're struggling because they expect you to do your own research to find this information.
1. You should be able to identify these. Not being able to pay the mortgage, property prices tend to rise in the LR etc...
2. You would have to make some assumptions here, or use figures from a bank. Go to Commonwealth Bank's website and see what kind of mortgages they have available, the interest rate, is it floating or fixed? etc do an annuity calculation to see how much it is monthly and see if this person would be able to pay it. Assume how much rent the 2 other students will be paying. ... etc
3. Research this. Get a loan, what kind of loan etc
4. Well this depends on what you decide for Q3.
I think you're making this harder than what it is. You just have to do your research and make assumptions then draw conclusions! There will be no 'right' answer. Obviously some responses will be more valid than others, but the bulk of the marks will come from doing your own research then being able to explain it properly, do relevant calculations properly, discuss relevant theory and concepts then draw conclusions to give advice to your friend.
Good luck.