I've also read conflicting advice on valuing a buyout amount, if you take the net proceeds of a sale and split it in half or if you pay half of the appraised value minus the mortgage debt. 

You could talk to her and ask her once she's caught up if paying half on the 1st and half on the 15th is easier for her, but they MUST be paid on time.This may sound harsh, but you said "She has 3 children, and he bailed." 

Time Requirement.You must spend more than 750 hours in real estate activities during the tax year.And you must spend more than half of your personal service hours in real estate activities.3.

Then he offers to fund half of the $91k so I can trust him and will give me 10% then 12%.

One of their tenants was one of their maintenance guys but was not their manager (making sure rent was collected), I think he paid either half of what rent should've been for his unit while the unit next to him was a 1bd unit as well renting for $650/700 at the time and that was about market rent still.

He had no children or wife and is only survived by my mother who is aunt and a half brother.

Someone on the West coast only cash flow is when you pay cash or half or more down.. mid west minimum down can and does create positive cash flow. 

A lot of people we first speak with favor the idea of a 15 year because they pay less interest over the life of the loan, and it of course cuts the term in half. 

I looked around the comps within a half a mile distance.

I would play along and let the neighbor know that you are sorry they need to sell their home for these health reasons and offer to buy it for half what its worth.