I found out that one of the tenants (family with one kid and another on the way) earns more than I do at my job (they probably make between around $45k between the two of them), and in the other unit, it's a couple with 3 kids and a dog, where the mom works full time (in a department store) and the dad goes to community college and gets stoned at home during the day (but I have no evidence of that other than personal observation when I repair stuff over there).The point is, as each week passes and I lose money paying for the loan on this property, I feel PWND.  

(2) Landlord will NOT pay to repair the following items unless caused by Landlord’s negligence: (a) conditions caused by Tenant, an Occupant, or any guest or invitee of Tenant; (b) damage to doors, windows, and screens; (c) damage from windows or doors left open; (d) damage from wastewater stoppages caused by foreign or improper objects in lines that exclusively serve the Property;I assume the toilet was working fine when the tenants moved in and at the stoppage is just located in the toilet, then this is something that was caused by the tenant or a guest and at the tenants responsibility.The only time we would charge an owner for clog is if the sewer line is collapsed and is usually evident by roots or mud in the line.If the sewer line is fine and any clogs are deemed the tenants responsibility.

I look for evidence that a person is academically serious and not there to party. 

It is, however, 100% incompatible with many proper EPA-registered disinfectants used in mold remediation, and very effective in cleaning up visible evidence of mold while not actually removing the problem.

Do you have evidence of photo ID?

Since there is not really enough evidence for them to take any action, you can also ask them how to protect your personal property in the event of police action. 

The message will become evident. 

If they have turned them off that can be very strong evidence that they have abandoned the property in a judge's eyes.

Does the ADA note that a person can just say that they have a disability without any evidence?

The last thing you want to do is accuse one of your employees, without a shred of evidence, as a couple of posters suggest.