I actually work with a lot of management companies and they tend to range from 6%-10% from what I see, but some of them also offer flat fee management (I know one in town that does a flat fee of $250/month.)
I would say there is a get what you pay for aspect so I’d interview a couple and ask the percentage, but also what it includes.
For instance…there are ones that would include the advertising in the percentage and others that would charge a lesser percentage per month then charge you for the ads.
I would mention that the majority of them tend to use Craigslist pretty heavily to find tenants and I believe most tenants go there first too. If your up to it and going to be in town you might want to think about finding your own tenant. I have heard some good things regarding American Heritage and they are a larger management company in town.