The realtor's communication with this tenant does not seem to be helping. 2) If she actually moved in, it is 95% likely she may have additional tenant protections due to her age and medical condition.

If they're not able to close themselves, then they definitely need to tell the seller that.If I have no intention of closing a deal myself I tell the seller that and enter a non-exclusive option contract with them so they can continue to market the house themselves.

Also in addition to vetting a deal sponsor, take an alternative route and ask that are currently equity partners in someone else's deals as to what their experiences have been so far.

The additional numbers and info you provided look good if it all goes to plan.

It's 2 bed/1 bath each, and it's on a 10,000+ square foot lot with parking for 4 cars (two garage, two additional off-street). 

There's a lot of value add here, in addition to what's already there.  

Aggressively paying down the mortgage by supplementing the 500$ in cash flow with an additional $1,000 in personal income we would pay the mortgage of in approx. 10 years and save more than 120K in interest payments.

In regards to the Borrowers’ front-end ratio, does that figure not take into account the rent cash flow that would be coming from the additional units? 

I know a lien or unexpected issue could hinder selling the property quickly or add additional costs.

In addition to understanding ARVs I have implemented some fantastic software for my company that has all the built in metrics that allows me to create ARV reports in a snap.