I don't have answers for all your questions but my opinion will be as long as you disclose to the sellers and they understand that they are selling their asset in a deep discount ( in your case $18500 vs $60K value) you are fine. 

A settlement statement was not provided or signed during the closing, and the fees disclosed had changed.

In my not so humble opinion if the managing company will not disclose how much kickback money they get from a vendor you need to report them to the licensing authority, and demand every penny back from money they did not disclose. 

Ok I will make a  calculation of the rate of closed deals vs/ offer made and I will keep you posted - honestly there is also another consideration that I need to disclose to be correct: my partner is a realtor and this many times facilitate the transaction with other realtors 

I am wondering if I need to disclose these hypothetical health concerns to my tenants.

They disclosed it.

The lender still needs to disclose the buy down and the loan origination fee.

Be honest, how often do we see anything on SubTo speaking of disclosing and all that?

The parties acknowledge and agree that neither party shall have any liability or obligation to the other with respect to the matters set forth herein unless and until a definitive PSA has been executed and delivered by both parties.ConfidentialityThe parties agree that all information exchanged pursuant to this LOI and the negotiation of the PSA shall be kept strictly confidential and shall not be disclosed to any third party, except as may be required by law or as necessary to obtain third-party consents and approvals.We trust that the terms outlined in this LOI are acceptable and look forward to your favorable response.

By disclosing your intentions, you’re covering your bases and staying on the right side of the law.Professionalism: Presenting yourself as a professional wholesaler can actually work in your favor.