I suppose this could happen with any seller regardless but I am also concerned given his age and ill health, what if at the time of purchase his interest in in probate or held by surviving family? 

To cover myself, I added the following provision to my lease..."... when needed to water the grass, Tenant agrees to allow use of their paid water to maintain lawn health and appearance as needed."

Again, not mandatory but seems to be more common as the concern increases about the health issues related to cesspools.Mark

The other part of this puzzle is his mental health.

I have worked in mental health for years and we regularly receive permission from clients to use their likeness in promotional materials.

We needed a permit and to be registered to remit room taxes (the name of the permit eludes me at the moment) and we also needed a health inspection and permit from the Health Department.

About 4 or 5 years ago he had a health scare and once through it we decided to write our agreement and each sign it.

I was the flooring dept. manager at a home depot in NH, i used to run the tile clinics for 3.5 years.

Tearing down hazmat is different than a regular demo job so depending on the county you may have some extra costs on that side as well.Testing, clean up, and certifying costs can get really pricey really quick if you're going to do it the right way - but even after you've got it passed off by the health department, you will still have to disclose the history to renters of buyers. 

This tenant is extremely high maintenance and everything is a “health issue” because she has bad allergies she says but she has two cats and her apartment is a mess with cat pee and vomit everywhere.