At the moment I don't have a concrete answer to your question.

Much of what was written just a few years ago can now be dated, non-compliant under Dodd-Frank and new tax law effective this year.

Concrete floors are a brilliant idea!  

Offer was based on receiving verifiable repair estimate)If using the 70% rule, $50K (or mid $50K) might be justifiable but not without concrete repair estimate.

I'm passionate about learning, and taking knowledge from a conceptual idea into a concrete reality.

Failing concrete is an issue all over the Caribbean, especially in Communist-era construction.  

That structure may require concrete and a rat wall.

I did a majority of the work myself (tiling, painting, concrete, landscaping, demolition, carpentry, etc.).

If you want to make their life easier, offer to replace the toilet with one that is chair height (also known as high boy or ADA compliant).

I've laid hardwood floors, tile (both on walls and floor), wired entire floors, plumbed entire flloors, framed entire floors, built a pole barn from the ground up, poured concrete, hung and finished sheetrock, etc, etc.