How much do you pay your property manager?

[Raymond Atzbach]

I'm just curious as to some average costs of property managers (around the Augusta GA area). I have been looking online and it seems most places charge you 10 percent/month, including a month's rent whenever they find you a tenant. Is this legitimate? Unless my guesstimate is wrong, that's almost 20 percent of your income/year you are paying in order to have a property manager! 
Is it worth it? Or am I looking in the wrong places?