The defendant has not paid the rent.

You could still be some what selective but it would be difficult to defend in court to allow one tenant to have a pet and deny another.

Since it is one word against another, if you go this route, you should be prepared to defend the action in court if it gets to that.

In my experience here, many Judges will ask the defendant if he owes the money and if they say yes the gavel will fall and the next case will be called. 

Sometimes tenants lie when they hear about a changeover and said they made payments when they didn't etc.It's easy for them to throw the person that is gone under the bus because they are no longer there to defend themselves.Not saying that is the case here at all but tenants try to manipulate anytime they see an opening. 

I reject anyone I do not want for any reason I choose and am always able to defend my decision but surprisingly have never had to.

Without knowing what the monthly rent is, the $500 fee plus the 2 months sounds a little excessive and would probably be difficult to defend in court, and collect if they just walked without paying.

@Sean Chen By the way if your neighbor tries to sue you there may be a clause in your landlord's policy that your insurance company will provide an attorney to defend you.

Neighbour As dog provoked the fight, neighbours Bs dog was only defending itself and neighbour A got in the way. 

And I think that criteria is defendable.