I think your best bet would be to check out local companies that do this kind of property management.
A reputable Company would likely be glad to provide references from satisfied property owners using their services. This would also allow you to drive around and look at some of the properties they already manage just to get an idea of how well they're maintaining them.
Try to get a sense of how often their rentals turn over- longer term tenants indicate more thorough/careful selection of same by the Property management company.