Whats the harm in adding him to the lease? 

They haven't moved in yet so no harm done re security they will just need to bring that before they move in. 

The proof you need to remove this condition from harming your loan approval will be to prove that you were "not," obligated on this debt that is current going through a modification or shortsale.I saw that you mentioned "currently going through modification or shortsale," if they find that you're obligated on this note/debt then your loan may be shot depending on what the verfication of this mortgage comes back with.Here are the steps the underwriter will probably ask for:- ask for mortgage note to see if you're obligated on this debt- run title profile or obtain a title report to see if you're on title- then run a VOM (verification of mortgage) to see what the mortgage rating and payment history has been on this mortgage (if you're obligated)- update the file accordingly and run the file through the current guidelines to see if you still qualify

The vapors from those chemicals probably is harmful.

What is this person doing to harm others?

Excessive noise can violate a tenants right to enjoyment here is the new York lawExcessive noise and vibrations violate a New York State law known as the “warranty of habitability.”

of ALL improvements (whether preservation or otherwise)The cost of casualty insurance premiums, plus 12% per annum interestAny improvements made after the redemption demand are not recoverable by the investor.All rents collected or earned before the redemption demand may be retained by the investor.Knowing this, especially the information about preservation improvements, should make you feel more comfortable about making tax sale homes habitable and rentable, even though there are still outstanding redemption rights. 

Since I have no idea what I'm doing, I have no bad habits to annoy you with.

The protests were 95% peaceful, with 5% making the news as violent scofflaws looking to harm people who have done nothing wrong.

I won't harm animals with my super suit... but I will be evil!