More broadly speaking, what strategies do you utilize to find off-market properties aside from mailing letters/cards, advertising on social media as "I buy houses", connecting with wholesalers and checking expired mls listings?

I follow them on social media and have spoken to them a few times about a deal prior to the pandemic.

Is there a better website or place on social media to get a tenant for my property? 

For example, are you experienced in social media marketing?

They're going to quit, and their supply will be out of the picture.When things aren't going great, there are two types of investors.1) The kind that rationally examines the market and forces at play, looks at what they're doing and how it relates to that and how they can succeed among that2) The kind that irrationally blames everyone else (usually politics), throws a hissy fit on social media, and loses money to spite themselves instead of looking at things rationally. 

I am a self-employed social media manager and real estate is my spirit animal.My goal in real estate is financial freedom, passive income and to travel mainly around the US, and/ Canada.

I have already done a phone interview, observed them during showing, had them fill out an application and called their references and checked up on their social media.

Employment, rental history, social media and credit and BG.

This keeps track of that check or electronic payment that gets sent out. 

Several of my contractors weren't able to cash the checks from Pen Fed due to electronic ACH from the credit union to another bank.