However, there are many others who's lives were destroyed by relying on the advice of an ignorant fool.  

Tenants, over time, have destroyed everything else that has been in there: wood, carpet, vinyl, laminate...everything.

Knowledge is definitely power and ignorance destroys. 

The key here is to keep them from destroying your house. 

These tenants have basically destroyed the property so we are ok with this.  

I tend to think it best to stay away from HOA situations.I literally ran into a buddy today who has a condo in an HOA and is going through a nightmare scenario of a roof leak that has destroyed a couple interior walls and is very costly to repair.  

Grow your war chest my friend, no one tells you about all the downsides to owning rentals, tenants leaving, tenants destroying your property, lawsuits, evictions, chasing rent, capital expenses, etc.

It helps NO ONE for them to buy a house for 70K that was worth 20K, have a ton a problems, get discouraged, the house fall into further disrepair, go vacant, and it further destroy the neighboring property values.Just tell them the truth, and manage the expectations..  

If a mark-up doesn't destroy the deal the question of what you could have gotten it for is mute.

they destroyed it on the way out.