I always print out everything and bring it with me as proof. Rental agreements, payments made, confirmation #'s, names, phone numbers, etc, etc. After 15 years of traveling to WDW and dealing with resort management at 22 of the 28 resorts, I'd be willing to put my entire reputation on the line that Disney isn't going to put a family out on the street due to some sort of rental scam from David's. I recommend using a Visa or Mastercard to pay, that way if you ever get scammed you can call the credit card company to report fraud. Most times they will immediately make the funds available to you while the case is being investigated. Then at least you could book a hotel somewhere else. Something similar happened to me about 10 years ago... I bought some park tickets on eBay that turned out to be used. (talk about a nightmare and a big lesson learned) I called Visa, they credited me back the $900 and I purchased tickets at the gate.
And you are exactly right, if David's ever had an issue with an owner trying to scam a renter I'm 100% sure you'd read about it online.
Now back to packing!!!!
WDW tomorrow!