Useful life and salvage have nothing to do with it, you depreciate over 39 years (unless you do a cost segregation study, in which case you can pull a bunch of it forward). 

I don't see tax relief on money not made to be super helpful.Tax credits - How would a PM or owner prove what they didn't get?

Would you ask the tenant to provide anything that proves they really need the help? 

People are equity rich, not tapped out.Here is the link to the full article if you want to take a gander: https://www.keepingcurrentmatters.com/2020/03/16/5-simple-graphs-proving-this-is-not-like-the-last-time/?

Keep all the receipts for anything you buy for the house so you can prove what you bought.

I'd like to find a sample contract that I could create so that the lender is protected and I have a promissory note that holds me accountable and that proves where the money came from when it comes time for refinance (and taxes). 

Having a relationship like this can prove to be very lucrative and allow you to seize these opportunities.

For those investor whom have followed this strategy or have studied it, what would be your best advice in order to be successful?

We just started this AirBnB in October, so would we have to file our taxes first to prove that we have a business?

Can they prove how long it takes to rent a vacant property?