Ironically, the property manager and the insurance carrier are not included in the lawsuit.

It's ironic how I wouldn't waste any $ on pull-tabs because a 1-in-28 odd's seems idiotic to shoot for but a 1-in-100/200/500 "what if" is something that bugs at me as a real potential and concern. 

Kinda reminds me of that grant cardon character, though swarmy seems less flamboyant (and consequently less ironic.)It's not just about the cash flow you can get today, it's also about long term security.

The drain cleaner snakes or jets the line and rarely are they able to see the items flowing past.Also in some cases it's a combination, it could be an old cast iron pipe with a rough inside surface full of rust, which started to act like velcro to things that flows past, or a slight settlement causing a belly, which again impedes the flow, then the tenant pours down grease, pasta and bean, well, you get the idea.Most of the time you end up eating the cost especially if the plumber can't tell you anything.Now, you mentioned that the clog caused water to back up to a vacant unit next door. 

I am slightly concerned about the age of the house and what lies under all the sheet rock (possibly cast iron plumbing, old electrical, etc...) and don't want to be held responsible for someones child dying due to my neglect of DD and the house burning down.

Currently here in Western Australia we are in the middle of a crash in iron ore prices.  

I'm good with people and like to handle the unusual deals with tenant or owner problems that need to be ironed out.

Have iron-clad criteria. 

If I am certain that it isn't my problem (ie collapsed drain line or corroded and scaled cast iron) then I pay for the first unclog on a drain and the tenant pays for subsequent unclogs of that same drain.

Ironically one of my best tenants currently also an attorney.