What about supplying a plunger for the house?

Giving your residents a quality plunger for free may also be a good idea.Next, you need to know why the toilet is backing up. 

Inside if you have roaches inside used Advion gel bait. advion 383920 4 Tubes and 4 Plungers Cockroach German Roach Pest Control Inse, Brown https://www.amazon.com/dp/B00730QW70/ref=cm_sw_r_cp_api_glt_fabc_HWAECYQJ2REY5WN1WPH8Bifen IT Spider Ant Scorpion Roach Spray Conc 16 oz Bifenthrin -NOT FOR:NEW YORK ;from#americanpestsupply https://www.amazon.com/dp/B01LWE9PAS/ref=cm_sw_r_cp_api_glt_fabc_ETZBJDSFG7608QV5HW5B

You need to plunge it, I said.There are 3 plungers already (left by previous tenants) that I distributed among the 4 bathrooms, but of course, his is the one without a plunger. 

Sometimes putting pressure using a simple toilet plunger will clear a clog. 

The amount of pressure caused by the plunger ruptured the bottom of the paper-thin galvanized pipe and let all the water out between the walls and down into the basement.

@Sharon S. if it is a toilet they keep clogging, then buy them a plunger!

Are you familiar with a plunger and how to successfully operate one?

"Real and consistent" as in all the paperwork needs to line up, no "oh his rent was $27 cheaper this month because he purchased a plunger" type stuff. 

And, after that experience, a process was put in place to ensure that all tenants sign-off on the initial walk-through checklist, that all repair requests have to be submitted by email with photos, and a "tool box" is provided that contains a plunger, hair removal comb for bathtub/shower drains, instructions on how to reset the garbage disposal, etc.