In Australia my property is managed by the estate agent totally. For each lease (generally 12 months) they get week payment (that was $500 or around HKD$3500) then they get 6% of the rent or around HKD$700/month. Total for a year is around HKD$12000.
The agent manages it totally, replaced a leaking tap the other day and even organised fly screens on some of the windows! She even sent some mail to me!
I'm happy to pay this service.