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? 

What is your specific concern: the smell will bother other tenants (if multis) or that it could turn into some sort of drug lab?

If they're concerned I'll lose some or all of the account value at the same time as I default on the loan, they could roll the contribution money into an identical account at their institution where the only investment option is cash (or whatever they consider safe enough). 

Yes I have considered the rent to own method.

It is also the only method of finding those recently vacant rental properties that the owner might be willing to sell while it is vacant. 

I know that the method I mentioned is riskier and not in any way ideal, so hopefully, all this due diligence will pay off and the next deal won't have to be like this. 

I am concerned that because of my age and lack of money I will not be taken seriously by banks when trying to secure a mortgage.

Hi there, I am a new investor working on my rehab quotes. I am currently working on a property that has sloped floors on both the main floor and basement. Same side of the house but not sloping in the same direction. ...

If your PM is not licensed and/ or using this agreement that might be a larger concern.

I am interested in implementing the BRRR method in order to acquire more long term rentals.