Extremely rural is harder to sell simply because fewer people live in extremely rural areas.One of the weaknesses you show with your questions is that you have no buyers.

@Seth Borman This is the primary estimating stage to determine if it's worth it to walk the property.

I just have to be a contrarian here @Caleb Heimsoth  as Caleb states I cannot think of anything risker than remote rehab for beginners.. keep in mind the author is a very experienced real estate professional and what works for him simply is not germane for beginners I know they want to sell books on this site.. but I fear there is going to be some really sad people that try to do this and simply don't know what they don't know.. all to just save 5 to 10k  extra that a flipper that does all the work and takes all the risk makes bringing you a finished product.. you can lose 10 to 20k in a heart beat doing this if not more.. 

Low income tenants were very difficult to deal with, because they simply didn't have savings and any emergency resulted in them using rent money, with the idea that they'll catch up before the eviction was finalized.

I'm offered an investment offering outsized returns (20% preferred return over 90 days), and wondering what I can do or ask to determine whether it's a poor choice of investment.

The deal determines how you will sell it and, if you buy right, you can sell pretty much any deal.You should be attending all your local investor meetings - go to MeetUp.com - to find what investors in your area are looking for, what they buy and where, how they find their properties, etc.Over time you will no doubt wholesale, rehab, hold rentals, etc. all depending upon the property you find as well as your finances at the time.

My question is have you done research to determine the market value of this property. 

During these walkthroughs we determined items that are in disrepair and fixed them. 

@Hai Loc I'm trying to see the build out plans to determine plan B.

If it makes a positive cash flow since day 1 price is not that a price should not be the only determining factor in a long term investment.Are their any leases with the existing tenants or does it have any obligations that you would become obligated for.