They got “smart” and charge you a constant fee whether you ever flush or not. 

Also if you were to take this route they will still go to the bathroom somewhere, it just won't flush away and they will be much more likely to trash the house worse than they already have.

Stick with cash investments and/or only invest in companies (stocks) that are flush with cash. 

Life savings flushed in the toilet, families torn apart over finances, embarrassment, losing all trust, etc... 

Flush all the toilets.Check all the outlets and make sure the plugs stay in and that the outlets are functional (note any switched outlets)Test the smoke detectorsReplace batteries in digital thermostatsMake sure all light fixtures are working (we replace bulbs with leds).Make sure there are thresholds and not rough flooring edges.Make sure the HVAC system is functional.At your move-in walk through: show your tenant where the breaker box is and how to reset a tripped breaker.If you have old triple track or double track storms, show the tenants how to operate them.Show tenants how to relight the stove pilot light.Test the smoke detector in the tenants presence and show them how to replace battery if not a sealed unit.Show the tenant how to operate the thermostat.Remind the tenant to use the bath fan or to open the bath vent window.

It requires a tenant flush enough, and willing to do.At signing of 1 year lease first month or a proration to the first, and one month's security deposit.

Now if you have a plumbing defect (say  weak flushing toilet) then I would fix the problem not the effects of it. 

I think sleep flushes beta-amyloid and tau proteins out of your brain.

The p.a. flush issue is negligible (takes 10 mins if you plumb it with foresight).

That a tenant will flush concrete mix down the toilet!