I chose to avoid garbage disposals altogether for similar reasons to the fridge ice maker, and I also chose not to put a dishwasher in the upper unit of my duplex because I want one less failure point for water intrusion and I didn't need it to have a competitive rental in my area.4.)

The commercial brokers give you a rent roll and a T-12 with the offering memorandum, but it is all garbage anyways.

I've also heard people say it's better to not put garbage disposals in rentals because it's easy for tenants to clog them, etc.

Garbage in - garbage out!

The worst part of the entire situation is not the fact that these wannabe "investors" post their garbage it is the fact that many sellers are victimized by them because they represent themselves as "buyers" and nothing could be further from the truth.

Would having an umbrella coverage do me any good and avoid me having to decipher which pile of garbage I should and should not step in?

Their Rooter plumber's bill for a "new garbage disposal/seals and to fix the leak installed" is more than $500. 

I only cleaned it out by ordering dumpsters and tossed out garbage and ceiling debris.

This is why large ranch homes tend to be expensive.At this part of the project my every day job was to focus on the following items, basically the same as a remodel, just in much larger volume (meaning more hours of my daily time):- materials: uninterrupted supply of the right materials just in time when needed- contractors: make sure the right people are on the job at the right time, discuss next steps with every one - every day- quality control: inspect the work of every trade every day, discuss issues and follow up with corrections- clean up: it's amazing how much garbage a job produces. keeping the job clean means higher quality and keeping it safe.- paperwork, tons of it: orders, delivery notes, invoices, checks, payments, lien waivers etc.About contractors: working with the right people makes all the difference.

Bigger complexes bill garbage this way all the time- flat rate per unit.