Since when do you have to sign a contract in order to view a property?
She already showed the property to the Seinfelds twice.
First of all,I'm not expressing any judgments regarding the question of the basic legitimacy of Seinfeld's lawsuit. I've bought and sold several pieces of residential real estate in my life...in several states.I've found that state laws and regional customs vary from state to state.In all but one incidence,I was required to sign a contract with an agent before he/she would represent me as a buyer.I don't know how things are done in your neck of the woods.
As I said earlier,it was completely reasonable for the agent in question to refuse to work on Saturday (or Sunday...or any other day of the week).
But I think that it was reasonable for Seinfeld to expect his agent to work on Saturday unless he was specifically informed that she wouldn't.Whether or not her refusal to work on Saturday constitutes some sort of breach of contract (assuming that he wasn't informed of her refusal) I don't know.
However,I do know that,particularly in a hot real estate market,a single day can make the difference between getting or not getting a property and can sometimes even decide the interest rate you pay on your mortgage.