It is not going to work that way.

Management fees can be anywhere from 5 to ten percent of rent, and repairs will be separate.

It is very easy to see why it does not work the way you think: If there is some repairing needs five hours' labor, 20 dollars per hour, it would be one hundred dollars. What about something he cannot fix? He has to find someone else, do you expect him to pay for you?

For this case, you probably end up like this: you pay him $50 per month for property management. Any repair/advertising/utility/insurance costs incurred will be on you.