You will NOT surprise me.I do have 'hard stops', 3X rent = income and no evictions.  

I offered her $21,000 cash and to my surprise she agreed.

Surprised no one in escrow discovered this as you said.

@Marci SteinI'm surprised the inspector could not observe that himself. 

I ran those numbers based on my worst case assumptions: Paying full asking price, preparing for unexpected initial repairs, maintaining current rent, and just guessing at the insurance.I believe I could potentially the increase the ROI by increasing rent to 1100/mo, not needing the initial 5k in repairs, and acquire for less.

I'm in cheaper NH and 15K is just barely enough to do everything yourself with a fourplex, leaves nothing left over for anything unexpected, and you have to live in the property. 

Next if you have $100k to spend you will need to also add in closing costs, including inspections and appraisals for each home, plus you will want to have a reserve for the unexpected.  

I would definitely not be surprised if we didn't get it.

I always thought first, last plus 1 month security is a lot but it works in some places and I would not be surprised if it was asked for when I was renting.

There's some strange and unexpected things happening with one of the GFIs in one of the units and it affecting a common house GFI in the basement that is wired off a separate panel.