If you are coming to Oz to work, I'd recommend you avoid using these type's of agencies. Yes, they will find you a job easy enough but it's much better to go direct to the recruitment agencies themselves (Of which there are many)
What these do is use a loophole in the Australian Tax system to claim a Living Away From Home Allowance (LAFHA) on your behalf, for this 'service' they deduct 12.5% 'management fee' from your weekly salary (Which they conveniently forget to tell you about when you sign up or detail it in your weekly payslip )
They use the LAFHA amount to pay tax at a much lower amount, and so there's less for you to claim back
Just a warning for all you hard up travellers.