If the letter is being returned, could that mean the property is simply abandoned?   

I would recommend simply networking as much as you can, attend local investor meetups and leverage your knowledge as an investor to better serve investors as an agent. 

If you try to inspect and verify, she will simply hide the evidence or lie and say he just stayed over that one night.

I was simply honoring the terms of the contract.

@Emil Pinlac about the backsplash -- nope, just for aesthetics. 

If you want to master these 2, study these 2, wholesaling is simply when you apply these skill to real estate for the purpose of "horse trading".

What happens... if you do nothing and simply sell or rent as is?

Their lease is up before January, I'm not sure if I can non renew, or if that would simply encourage them not to pay and then fall squarely into the eviction moratorium.   

I’m looking for other real estate investors/wholesalers in the Pittsburgh area.I simply need to surround myself with other like minded people and build business relations because I am a rookie to all of this!

You would ideally want designs that are aesthetically pleasing but also have long term durability.