I've reciently been in the same prediciment. I live in the South eastern suburbs of melbourne and it has taken my boyf and I around 3 months to finally get approved for a place. We both have full time jobs and earn over a $1000 per week between us..
There is alot of competition, at some houses especially in narre warren/berwick there would be 20-25 other people looking at the same property.
We are both 23 so that didnt help either! So we increased the amount that we were willing to pay by around 10-15 per week, which meant there was less competition.
All you can do is keep on applying..Make sure you add a good reference from work, and If you have some savings perhaps offer an extra months rent in advance...
Also do you know anyone who works for a real estate agency or know of anyone who knows someone who works for one? That can help you alot as well...
Good luck, try and stay positive, its hard sometimes I know but its better than getting upset over it.
Im moving this w/end YAY first time moving out, will be awesome, a little sereal but am looking forward 2 it!