Self managing can, from time to time, take time as well as money. That time is not always at a time which fits in with your own schedule.
When I self managed I found it very hard to fit things onto a schedule which was already quite busy.
People can be turned off as it is by having the landlord living next door. Self managing will make this worse.
You also don't want tenants knocking on the door at midnight asking for a light globe.
Having a PM can mitigate those things.