Hi Ajay,

I am a property manager in Victoria (not sure which state you are looking, it does vary from state to state), it is quite rare that an agent will have a flat fee that covers everything. In fact, you can actually be worse off if you sign for a flat fee. Common fee structure is:
7.7% management – includes distribution of funds, collecting rents, financial statements, organising maintenance, routine inspections, lease negotiations and basically anything you can think of that needs to be done to look after a property, both landlord and tenant
4.4% leasing fee – is ONLY charged if a new tenant needs to be found, so if you have the same tenant for 3 years you wont need to pay this fee for that three year period. This includes all lease preparations, application processing, open for inspections and so forth

These fees can also be negotiable, but keep in mind that lower fees doesnt mean better service. You will get what you pay for! Sometimes it is worth paying a little more for a boutique/upmarket agency to manage your property.

I hope that helps. 

Courtney