Maintenance costs aren't just holes in the wall, you have to be thinking about long term stuff - water heater, furnace, a/c, capex fund for large replacement/repairs, deductible on insurance when there is a large storm, roots in sewer, etc. Might only pay $500 in first couple years and then $10k in year 3.
Management cost should always be included as an expected expense, in this case think of it as paying the 10% to yourself. If you keep going down this path and have 10 rentals and decide that you need to hire management all of a sudden the number don't look very good.