I use a property manager so even though it's little things like replacing the weather stripping on the door And unclogging a toilet anyone with a plunger could unclog I have to pay fees.

Instead of looking at loosing 10% profit by having a PM consider the benefit of not sleeping with the golden plunger.

The doorbell is probably an AC solenoid doorbell, which means when current flows through the solenoid, a magnetic field is generated, thus creating a force which pulls the plunger to the plate (ding).

I do advise a plunger.

We recently encountered a problem when a sink backed up and a plunger was used to clear the clog, it loosened the sink mount, which added to our woes.

Help your tenants keep clean by making it so they can clean as lazily as possible (provided: washer, dryer, dishwasher, vacuum, a plunger in each bathroom).   

Tell them to buy a plunger or provide one.

Tenant agrees to pay for clearing the drains of any and all stoppages except those, which the plumber who is called to clear the stoppage will attest to in writing, were caused by defective plumbing, tree roots, or a result of weather.Tenant agrees to keep on hand and properly use a plunger when necessary to unclog drains and to prevent water overflow from toilet, sinks and bathtub.

part of your responsibility is at move in to show them how things work,, how to turn on the heat, how the smoke detector works, how to provided a toilet plunger with the apartment so if they have a minor toilet clog they can fit it themselves,, and show how to use it, where the electrical panel is an how to reset a breaker,.... the stuff ordinary people would understand but renters aren't always ordinary people.Get a system for contact for repair requests,, have them text or leave on voice mail ,, don't go and answer each call right off the bat,, give a thought... call back and try and trouble shoot with them over the phone... as for toilet and drain clogs I'd let them know if plumber comes out for service if it is found that clog is from food, toys in toilet,, or grease they will be charged a service call. some use a form for this at move in. 

Penalty for going over a month.Lease renewals same fee for filling vacancy (put the focus on tenant retention).Education program for tenants to teach them how to change batteries in thermostat, flip breakers, provide plungers, reset GFCIs.....