To me, this is a red flag.

Not every inspection request is a red flag!

In my leases I put clearly that if a tenant flags a request as emergency and it is determined to be their fault or not an emergency they are responsible for the cost.

Would you have any recommendations, in your experience, for what to look out for in the documents that would be red flags or items that would negotiable?

The only slight red flag was that they only accepted payment via Venmo or wire transfer, but that's how I accepted payment when I was selling lead bundles, so I still thought it was worth a shot.

And are there any big red flags that make you walk away from a deal right away?

That says huge red flag to me.

We've only had one resident fail to pay rent, and it was someone who had all the usual red flags, but she also had a sick kid. 

Also look back on their application and see if you missed any 'red flags" so this can be a valuable learning experience for you.

I would not characterize this as a scam per se.. but it appears to me to be a failed investment model..