Either decision could cause you a lot of heartache and/or financial ruin.

This possibly ruined our deal or possibly not however he promised to close and now hes backing out of a package

I just tried to listen to a recent LSU podcast and I'm afraid BPs podcast has ruined me.  

It temporarily ruins your credit such that you have trouble for several months after you pay off the cards restoring a good credit score.

One day someone will have to deal with it and there is a danger it will get so run down that it ruins the whole street.

A colleague of mine didn’t have a signed contract/lease and the tenant took every lightbulb, cabinet knob, faceplate and ruined light fixtures in the 3 months it took him to have the tenant vacate the premise.  

Needless to say, the book did not do a very good job explaining how that can ruin a good deal.Lets say I bought a triplex to house hack in and the purchase price was 300k.

If you are talking about gable vents, that has no bearing on the roof installation, but lack of proper ventilation will ruin a roof and any reputable roofing contractor will not install/warranty a roof without proper ventilation. 

Bigger Pockets was one of the first resources recommended to me, and it's been a gigantic help.By way of background, we reside in Orange County, CA, and just within the last several months finally emerged from the smoking ruin of the Great Recession.

It will save you from getting into another deal with your expected profits and then facing financial ruin when they don't show up on time.