I have little experience in RE but see the importance of approaching our first joint purchase financially as opposed to emotionally. 

, financially independent as a landlord, career tenant/victim that sues landlords for discriminating against my emotional support chickens, retired, other (explain)Gross monthly income: $Monthly debt obligations appearing on credit report (this includes car leases), plus (if applicable) personal rent and alimony/child support/etc: $FICO: Excellent, good, ok, bad, you don’t want to know, not sure.Credit issues: Late credit cards, thin/no credit, Ch7 bankruptcy, Ch13 bankruptcy, foreclosure, short sale, etc, and how long ago the event was.Additional details: 

Defend your argument with emotion.

It is best to have them agree to this early on during lease signing rather than them take the route so many tenants are taking by claiming it as an ESA (emotional support animal, which is considered a service animal -- no additional fees can be charged for ESAs).

Don't be emotional about it, just stop talking and listen, its important to be successful.

It can be a bit of an emotional rollercoaster at times. 

From my reading of the OP, it sounds as if this owner is being too emotional regarding this house.

I understand your emotional attachment to the house, but it is no longer yours.

People are more appt to become emotional and join together if there is a common enemy.

Don't let emotions play a part in your decision.