They are just made up rules that were meant to help new investors run rough numbers on properties but I think they do more harm than good.You will be much better off if you just start actually underwriting deals.

It's more harmful than good, the level of benefit is networking.

First, do no harm is officially out the window. 

Over time, responsible financial habits will repair your credit.Your goal of 20 paid off homes by 55 is ambitious but doable if you start now, educate yourself, repair your credit, and stay disciplined.

Person harmed already filed lis pendens - they have to prove the case then get judgement then lien the property but the filing holds up refinancing or selling. 

I mostly do this out of habit, back when properties were being sold way above asking.

First develop a habit of doing it, taking actions, either fail or succeed, then learn and grow and continue doing.

They suffer no harm, you do.

Seller's credit harmed for 4-7 years.

Nonsensical policies by AirBnB that harm the hosts and allow bad guests to get away with non-payment4.