The extra costs should be negligible if you are renting out enough units. 

To me, it seems like outright negligent damage.

I would just be careful or sucks to spend the money on the unknown but it also sucks to need a new septic because of negligence by past owners.

This is negligible and would cost far less than replacing the septic.Easement was likely created when someone sold the lot behind the house. 

My educational background is in Geology and the last thing I wanted was an EPA violation due to their negligence and lack of maintenance.

Thank you reply :)I spoke to an insurance agent today that said dwelling insurance is 'more' cost than a home-owners policy - because risk that tenants don't care about landlords house and don't report leaks, damaged walls, and other negligence on part of tenants and/or poor property managers. 

If you completely fix up the house when you buy it, your short-term repair requirements should be negligible, so that would be your cash flow.  

If indeed the extension was because of the sellers negligence I think you would have a win. 

It looks like it is proposing that the attorney general can dissolve certain "public benefit corporations" if a corporate landlord is found to be negligent, and there is some pretty vague language about what is covered.

If it truly is caused by the tenant's negligence, then you should be able to bill her for it as in the lease it should say that the tenant is responsible for any damages caused by their own recklessness.