Those aren't appraised via income approach, they're appraised using comparable sales approach.

What is the best way to find and approach people who are not necessarily selling at the moment and make them consider a sale?

I think if you understand the price per unit as well as the price per square foot in the zip code and nearby zip codes that will give you a good idea of the comparable market analysis approach and appraiser might use.

It will be helpful if you get that lease resigned before approaching the bank.  

If we approached him with the $5,000 and had the deed put in our name, could we pay off the mortgage and own the property?

Take the 4 Hour Work Week approach and head off to somewhere in exotic😉

This approach requires more messaging though—and the impact of this at a larger scale could be a lot of extra work—but in our view, it was absolutely worth it.

When I came across this property, I approached the seller directly and negotiated a fair price based on the property's condition and potential.

This is more great info to put down on my list of things I need to ask when I approach the seller.  

From there, you can better transition into a DIY approach