Considering purchase of a hoarded property-what to look out for?

[Brad E.]

So I'm looking at a deal with that is for 2 houses on a single lot.   Both have current tenants which have been there 7-8 years and appear to be major hoarders.  When I went in to view the property cat urine smell hit me so hard I almost fell down.  I was so grossed out I wanted to burn my clothes when I left.  

Given the condition of the property I am not sure how to go about evaluating it.  You can't see the floor in most of the rooms in both houses.  

Any thoughts on how to approach this and come up with my MAO? Should I just assume a total tear out all the way down to the studs?

Not sure how to know if there is anything even salvageable when I cant see past the garbage.  

Also, is there anything that I should be looking for specifically during due diligence related to the hoarding?  (I am guessing there are common problems with these type properties)