Tanent placement takes about 50 hours per deal on average. For the same $1250/month rental unit charging a full month rent, that is $1250 per deal, again $25/hour.
This applies to managing a typical 2-bedroom unit in silicon valley.
Note, property manager does not do any hands on repairing work. They do "vendor selection and oversight". If you can use your time to earn more than $25/hour somewhere, go hire a property manager. Otherwise, that 8% might be what you need to turn cash-flow positive.