It just feels like taking advantage of someone who may be slightly desperate or vulnerable.

You don't have to be outrageous or con anyone.These issues are compounded dealing with low income people, might as well look at these "buyers" as a protected class, they are seen as the most vulnerable, least educated or business wise who may be the easiest to take advantage of,  just a fact.  

I'm looking for investors to share what may seem to be a very vulnerable situation.

It will be the most vulnerable investor though that will get hurt.  

Burdened with a vulnerable and helpless feeling, I agreed to accept ABC Baltimore’s reduced offer of $95k and closed the buy—back with ABC (we still had to pay closing costs).

Personally, I think MF is extremely vulnerable and dangerous in the current environment..

I would just hate to have anything come back legally for taking advantage of the equity because the homeowner was in a vulnerable position. 

However, due on sale, series LLC vulnerability, and taxation under this structure is of concern to us.

If I am reading this right, you would be getting a home worth ~ $149,000 for $149,000 (65k loan + 84k loan), would be vulnerable to letting the bank use their option to demand the full value of the home now, and you do not think you could get any bank to give you a loan for the bank's full demand of $84,000 if this were to occur. 

Remember everyone has a frame of mind, the realtor wants to sell, the inspector wants to impress with his detailed findings, the PM wants to rent the unit out with as little effort/turnover/maintenance as possible - so you are able to get a detailed look through many different frames just make sure you are dealing with people you have researched and trust.I know how stressful it is to buy the first because there is a lot of pressure on something new - and only having one leaves the business vulnerable, but as long as the numbers are great and you do your due diligence then you should be fine.