I'm currently helping my aging parents, and I need to be spending more time taking care of them.

Our prospective numbers point to increasing profits as the deal ages with an eventual infinite ROI once the initial investment is paid off.

We are quickly approaching the Silver Tsunami of the boomer generation aging into needing assisted living.

A lot of this is due to the age of the homes (some homes here are 100yrs old or so).

Aging reports would be another avenue to explore, but again, may not even have these.Lastly, while maybe this property is in a desirable area of town with strong demand from highly qualified tenants, but I get the impression this is a rough part of town, with very limited demand from tenants.

So your number of 715k may not be too far off depending on the square footage and also the age of the cabin.For anybody to suggest otherwise without knowing more information on your specific cabin isn't giving you the best advice to be honest. 

The article you post is nearly 2 1/2 years of age. 

I built my first modern 7 years ago and like you agree that some (not all) moderns will age out.

We plan to rebuild, but our neighbors are aging and do not wish to go through a rebuild.  

I also meet alot of people in my line(s) of work and this seems to check out in my conversations with them, this includes natives, recent transplants, old transplants, every age group and race.