If it is on the line, then you would to sue with some form of an adverse possession claim (if your state has such a claim) based on the previous owners use of the property.

But there will be no guarantee one way or the other.I expect that somebody described as "the tenant from hell" will always be a bad tenant, and I expect that somebody who is a model tenant (especially through adversity of some sort) will behave well as a tenant.

I am primarily wanting to do rehab deals with an emphasis on providing solutions for properties with adverse subsurface and environmental conditions throughout Los Angeles.

To prevent accusations of discrimination in todays world, it is best to give an application to all interested prospective tenants, when you have verified the applicant doesn't qualify, you can send them a denial letter (Rental Application Response/ Adverse Action Notice).

It's the exceptions that will get a property hung up in underwriting... like checking 'Illegal' under Zoning Compliance or anything under "adverse site conditions" or "adverse conditions".https://www.fanniemae.com/content/guide_form/1004.pdf

What is the current rent roll not rent income how many vacancies, and what is the adverse market rent for the units in your area.  

But if that septic system has been in place for decades, you may have the right for continued use (even if it is on the neighbors property), via adverse posession.

We met yesterday and went over things and signed the listing agreement and I told him that there were a few things I needed to get done that might adversely effect the image of the listing if shown before they were fixed.

Adverse possession generally requires exclusive and continuous use.

I have looked at adverse possession laws in the state of Tennessee to pay the taxes and later just suit to quit the title to convey clear title.