There is no real good answer to your inquiry. I would say think of ways you can make contact with and interview other property owners that use PM COs.
Honestly other than asking others who do use property management companies in your area I see little you can do to keep from being exposed to Property Management companies that will over bill you or otherwise take more than is absolutely necessary for them to perform the function you desire from them.
Experiencing a high turn over rate for your unit or units is a common complain about property management companies. You could do your own tenant selection when that time comes but then again they may defeat your purpose to hiring a property management company in the first place.
Trial and error until you can find a good property management company that does the job in a cost effect manner for you.
If you set the criteria for tenants, they must get tenants that meet the criteria.
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