What methods did you use to acquire them? 

I have even bought properties with this CC method and sold them wholesale a week later.

You’re either conflating a different payment method than credit/debit(like giving direct non third party ACH access to your tenant to your account) or talking about a fraudulent situation with a judgement or you or your “someone” is being less than honest.

For Buy and Hold strategies, this method is far more superior than traditional financing of properties.

Find Brandon's videos on YouTube for the "four square" method of analyzing homes and practice.

This is a popular method to execute the BRRRR strategy.

Personally, I've never bought this way, but I have sold using this method.

If there isn't one website or source, what is another method other than looking at the competitors?

But if you have a little money to invest, then skip-tracing and contacting property owners is another method. 

I started with the BRRRR method for long term rentals.