The person who was the service person for my area recommended me another specialized handyman to actually clean up and close out a rodent hole near the bath drain.

You can see how much a 1-car garage vs a 2-car garage affects appraisal, granite counters vs no granite counters, etc.For example, in my market, granite countertops are a $5,000 bump in the appraised value.The inspection is more geared towards finding what's wrong with the property (what's not up to code, safety issues) and making everything is in good condition and working as it should (electrical is wired correctly, plumbing drains well, no mold or termite damage, structurally sound roof, etc.) 

They had to install system that cost about $80000, it is 26 space park, which consisted of 4 big media filters that alternate use and bring levels to zero and even have their own little drain field for the backwash water.

But I also don't want to drain everything I have saved to put 20% on something.

You can put a bucket under the kitchen sink but probably not under the tub drain. 

The grains of the wood act as a channel to drain water.

So far it has survived some minor floods while it sat vacant for a time (a leaking 50-gallon water heater and also some water infiltration due to a bank of snow outside atop a drain that wasn't working).For the price, I don't think it's too good for a rental if you own a nice rental, as is the case here.

With regard to frozen pipes, I find this statement strange because I've never seen a REO that have not been winterized (Main shut off, all faucets and valves are turned on and the drainage pipe are drained).

That won't test the sewer and drain lines though as I recall.The shutoff at the street level might be broken in the off position.

If you have to do any type of drain tile or sump pump to fix water issues, now is the time to do both, they put the mitigation system in the sump pump area so a contractor that  can do both might save you some bucks.