I can assure you as my wife and I are starting into the rental business that leasing a residence is not passive.
A cheap property manager or estate agent is generally not worth it - their main goal being to rent the property as quickly as possible to anyone, rather than ensuring rental to a good tenant.
Decent property managers cost a fair bit of money and unless you own the property outright or have a very low mortgage it's tough to afford a good manager and have a reasonable passive income from the property as well.