6 to 8 weeks prior to the anticipated completion date of your property, you can start seeking the services of a property manager. Its good to advertise for a tenant before you get handed the keys, as you may be able to get a tenant to move in straight away.
A good property manager can be invaluable for you and if well instructed, will undertake much more for you than just collecting the rent. They can pay any accounts like rates, water or any maintenance fees, and undertake periodical inspections to make sure that the tenant is looking after your property.