Great for moisture, fire and bug resistant reasons. 

I also build things into my design that I use as selling points—mold resistant/hypoallergenic, easy to clean etc.

Corian is wear resistant.

I some places (CA or near water) we have gross rats resistant to poison. 5 gallon bucket with plank and peanut butter works but you have to keep emptying and refreshing.

(in my Forrest Gump voice—couldn't resist!

Always on the lookout for creative investment avenues, we couldn't resist this perfect first project, especially with the added advantage of owner financing $100k at 0% interest.How did you find this deal and how did you negotiate it?

If not, any ideas/advice if I encounter resistance from them? 

We delved into the intricacies of structural repairs, electrical and plumbing systems, and the integration of fire-resistant materials to enhance the safety and resilience of the reconstructed house.Throughout the arduous journey, we encountered numerous setbacks and hurdles, which tested our resilience and problem-solving skills.

Plus depending on the building code in your area you may have to have the 5/8" fire resistant drywall between the units.

How are the rest of you resisting urge to sell?