The other 2/10 is a foreign object in the drain or someone really really flushed a massive **** ton of toilet paper."

It doesn't sound like a showstopper to me.Did you ask the plumber if there is anything people can flush that will help keep the lines clear?

installing PSL flush beamSome of my other favorites are undersized electrical services (particularly underground) aluminum and knob n tube rewires.

Apartment noises - neighbors sounds (flushing bathrooms from other units, sirens from street, etc.) 

This is the simplest method, but it also means your tenants are more likely to abuse the utilities by leaving windows open with the heat or A/C running, leaving lights on, ignoring the toilet that constantly flushes on its own, etc.3.

They were getting it flushed several times a year!

I personally know of top 1% Airbnb homeowners that are flushed.

This is the simplest method, but it also means your tenants are more likely to abuse the utilities by leaving windows open with the heat or A/C running, leaving lights on, ignoring the toilet that constantly flushes on its own, etc.3.

Anything with a class 5 rating flush would be fine.

This is the simplest method, but it also means your tenants are more likely to abuse the utilities by leaving windows open with the heat or A/C running, leaving lights on, ignoring the toilet that constantly flushes on its own, etc.3.