I have had terrible experiences with PMs in the past. I now interview my potential PMs with questions such as:
How often do you conduct inspections?
If we experience a large storm will you inspect the properties?
Are you willing to lower your fees as we add properties?
I now work with two PMs in two states and they have been great. The one offers a discount for assigning leases due to multiple properties. I also buy through my leasing agents which helps build our relationship. They know what I am looking for and they are able to provide the best assistance. The whole idea, at least for me, behind having a PM is to remove myself from the management process as much as possible. In past experiences, I found myself managing my PMs rather than them managing my properties. This is not ideal. So, working with a PM you trust and allowing them to make the call on repairs under a certain amount (ex. $300) works well for me. I am an active duty Soldier and recently I was out of the country when a water leak coming from the hot water tank was discovered in one of my properties. My PM handled everything to include the insurance company. They earned every bit of their 10% of repair cost fee.
Find a reputable, like-minded PM who provides value to your company. If the fees work for you then do business. If not, then negotiate. Once you find a PM that is willing to provide the necessary assistance at a price that works for you then try them out and do not be afraid to fire them.