That sounds more like a dream for him as an investor with no evident reason for him to accept a discounted price or terms.

He can then see who the culprit is, and report it to the police with video evidence. 

(IMO) It is unlikely "Rats" chewed anything.Though it might be intelligent to have your pest control person come out and look for evidence of the creatures.If it's found...remediate it.If not re-assure the renter and family that there are no rats getting inside.Possums, and cats under the houses, dogs running loose in the roads--a poor rat wouldn't have much of a chance.

In the county records I don't see any evidence that the county sent notices to anyone outside of the former owner.

Instruct me, I've seen no evidence of that, but maybe I've never read the instruction on how to flush.

You're not buying low enough if you're that worried about a plumbing leak, unless there's some type of evidence of a major issue under a slab.

If that doesn't work, deliver it by hand or tape to their door as evidence of delivery. 

Medical bills, older foreclosures or bankruptcies with a clear path of redemption, divorce, and other events...if the person is upfront and there is evidence to support significant improvement overall.

In a nutshell the responses were how to provide evidence of value to them.

It has become evident to me that real estate investing demands a distinct mindset, separate from that of a real estate agent.