when we said hey we are going to sue them.. their lawyer said they are judgement proof..

This is just my opinion,but being a contractor myself, it's not a very good way to build a lasting relationship with a contractor, not to mention if it ever got to court you would have to prove to the courts what the damages are and with no history (proof of income) for that property you could be fighting an uphill battle.

I initially read about this method for sound proofing, here’s a very detailed study: http://www.mjm.qc.ca/publications/en/177881_Floor-CeilingAssemblies.pdf6) A new method for air sealing an entire unit/home is AeroBarrier.

I offered to provide any and all requested documents (proof of funds, pre-approval, etc).

I plan on moving into a duplex and renting the other side out. When owning a duplex is there anything you can do to help cancel sound between the two units? 

@Kevin LefeuvreAirbnb will refund fully for certain things, and illness with proof of a doctors visit is one of them.

If interested they will ask you to provide proof of answers.

As we are not in town at the moment (my dad is sick in Canada), we wasn't able to further collect evidence to proof anything, and have to wait for our contractor to go back to the house to collect evidences.    

However, I don’t have any hard proof it was him.

If you can't provide proof of how you are going to pay for a property you are offering to purchase, why do you expect a professional to work with you, potentially for months on end?