The life of that base can be expanded by making it more water and chemical proof.All that being said, I'm not sure I'd charge the tenant for it.

Phase I: An assessment and report prepared by a professional environmental consultant who reviews the property, both land and improvements, to ascertain the presence or potential presence of environmental hazards at the property, such as underground water contamination, PCB's, abandoned disposal of paints and other chemicals, asbestos, and a wide range of other potentially damaging materials.

Also be aware of any chemical hazards, such as the remnants of a meth lab or leaking oil/chemicals in the soil.

Pumps, plumbing, filters, chemicals, etc.

Powderpost beetle treatment costs a bit more than other pest treatments, it requires some expensive chemicals. 

Can you just gut the unit and then spray everything with a chemical to kill the mold?

A little bit about myself; I'm a recent college graduate who moved out this way from the east coast last year, I maintain a "9 to 5" as an engineer in the Chemical Manufacturing industry, and I am looking at REI as a means to further diversify my portfolio.

Either the house is a tear down, there was some sort of toxic chemical spill, or something else is terribly wrong... right?

Chemicals and water loss does cost some, but not as significant.  

Unless the owner was selling the meth I don't think that would happen.I have also heard you might need to gut the house if meth chemicals are in the walls.