Wait until the first time you get sick from some mysterious disease because you were prepping a paint job somewhere in some filthy area and some decades-old bacteria were waiting for you to scrape them up.

Outbuildings didn't have to be touched beyond basic clean out.I agree with others who have stated that plumbing and electrical can get you, but it's so worth working with a jack of all trades general contractor who knows her/his stuff and you know codes so you can give very specific direction and have them get the job done without having to use a full-fledged plumber.The following has nothing to do with your question about biggest expenses, but may save you big dollars in the long run:We were given some tips that have paid off: vacuum out your HVAC system to the best of your ability prior to inspection (inspectors see dirt or dust and they give you poor marks and tell potential buyers that a professional needs to be brought in to clean out the system); run Draino through your tub/shower drains (if you're leaving existing tub/shower in tact) prior to listing and test the drains to make sure there is good flow (we might or might not have used the tubs to clean paintbrushes, which resulted in REALLY slow drains); If you have a hand dug or shallow well, run bleach through it (lots of instructions online as to how to get bacteria out of the system when a hand dug well is involved) and flush the bleach immediately prior to inspection.I hope some of this helps. 

It has taken me at least the past year to recover, go through cycle after cycle to make sure all the deadly bacterias are out of my system & that there is no threat...THIS IS MY TIME TO SHINE!!

That's like saying you want to remove all bacteria or all pollen. 

Then we sprayed the joists and remaining subfloor with a product that killed the urnine bacteria.

If he is truly deranged or mentally unstable (possible with neat/bacteria-free issues)....you may be able to send a contractor (or multiple contractors) over to the crawlspace and leave some unpleasant smells, take pictures, and look for indications of illegal drugs.

.:) Some day I'll tell you my squatter story, but for now...think I'll keep that one behind " lock & key " Thanks again Aaron for your views on the lockbox quandary & seriously, now in my 50's, the thought of seeing myself crawling through a dirty window possibly falling onto a nasty,stinky ,bacteria breeding carpet remnant scares me as much as the thought of who might be taking up temporary residence on that nasty, stinky....

According to its site: The Host Protection Insurance program does not apply to liability arising from (1) Intentional Acts including: (i) Assault and Battery or (ii) Sexual Abuse or Molestation - (by the host or any other insured party), (2) Loss of Earnings, (3) Personal and Advertising Injury, (4) Fungi or Bacteria, (5) Chinese Drywall, (6) Communicable Diseases (7) Acts of Terrorism, (8) Product Liability, (9) Pollution and (10) Asbestos, Lead or Silica. 

Good luck describing the complex world of human social interaction in terms of cells and bacteria.

They have bacteria that breaks the waist down and the overflow goes to a dry well area that handles the overflow of liquid while the waist drops to the bottom of the tank and breaks down by bacteria.