Its not bullet proof but close to it.  

The seller will want to see proof of funds like a bank statement or a pre-approval letter with your offer, so that they know you won't back out due to financing.

They haven't been a maintenance issue other than the glass shades once getting broken which I was able to replace with used shades from a used construction material store like Habitat for Humanity.

Are there any numbers or proof to these claims?  

This was a proof of concept that Midwest rentals can and do cashflow atm without the HELOC part and with more conservative numbers that was in the concept of a discussion with someone else.

This warrants its own bullet 3) horrendous underwriting

Having the other heir sign a quit claim so the paper trail is bulletin proof.

You remind me of the guys who go hunting with the giant 10,000+ candle power halogen spotlights that when stopped say something like there not shining the deer, there just illuminating a path for the bullet.... 

Generally speaking, other than a fire wall and additional sound proofing, what other costs come into play w/ duplexes or mfh in regards to that joined wall?

Under the IRS rules, a person  qualifies as a real estate professional if: (1) more than one-half of the personal services the taxpayer performs in trades or businesses during the tax year are in real property trades or businesses in which the taxpayer materially participates, AND.....(2) hours spent providing personal services in real property trades or businesses in which the taxpayer materially participates total more than 750 during the tax year.Like @Greg Scott and @Russell Brazil mentioned above, I don't believe that you would qualify as a REPS, but if you are going to try it, make sure you document it very well (i.e. with some kind of proof, like time cards, mileage forms, and/or receipts, etc.) so that just in case you do get audited, you at least have something to provide to the IRS agent.