Introducing a new tenant will necessitate an amendment to the existing lease, and you should conduct a thorough screening as you would for any new prospect.

The NAR settlement is not even yet approved so I would not be making any decisions based on a potential settlement that could be amended.

I need to hire a broker to process the application (with supporting information), counsel me on useful amendments to the AIR form lease and get the lease signed.

I shake my head at how they would contradict their own note unless you signed the mortgage or amendment agreeing to this.

Normally, for comparables, you want to look up recently sold properties within a half mile to a mile (the closer the better), in similar condition, square footage, amendities as the end product, and the same or similar bedroom/bathroom count.

They get that back 100%, one month free and a great referral to help them on their way, if they agree to sign a lease amendment shortening the term accordingly.

Last year, the State Legislature amended the Property Condition Disclosure Act, removing the option to give a $500 credit to buyers and adding seven questions related to a home’s flood history and insurance requirements.Here is the link to the story. 

That, or insist they amend the contract to include that language for you as a protection.

The deal, reached after a yearslong court battle initially brought by a group of home sellers in Missouri, calls for the powerful National Association of Realtors, which has long regulated the way U.S. homes are sold, to amend its rules on how Realtors for sellers and buyers are compensated.In most real estate transactions in the United States, both the seller and buyer have an agent representing them.

IMO It is a complete violation of the takings clause of the 5th amendment... but you're going to be in for a world of hurt if you buy into a market with existing restrictions.