Not worth the headache to letigate. 

Our listing agreement states the commission is earned (no owed) when a willing, ready, able buyer is secured.

Richie - I don't worry about it. If the deal does not close, I just move on.

If you are the listing agent...when a ready, willing and able buyer comes through with a full price offer and no contingencies. 

When a legitimate offer is turned down.

When a listing is canceled on a whim.

When a buyer gets cold feet and backs out without cause.

Of course for all of these, it is complicated... and an attorney may have a different list.

If I'm on the opposing side and they are in the wrong.

When the buyer is approved for the loan and backs out.  

in the real world? when it is done. besides seeking litigation. thats what retainers are for :)  unless its a reo , then you have ole money bags to sue perhaps

The answer to that is normally in the contract. If you produced a ready, willing, and able to purchase buyer, then your contract will state if you're due a commission or not.

OUr contracts say commissions are owed at time of contract--but in practice we don't collect until closing. And if deal falls through, it's not likely we'll ever collect. Can you imagine big local real estate companies suing members of the public for commission?

Usually never. I had an agent last year think he was owed a commission because he wrote an offer that was rejected by seller.

The terms of the listing agreement should address this type of issue.

When you fulfill your job.

This is case by case for me.  If someone decides to do their shopping for a lender AFTER wasting hours of my time picking my brain, using my expertise to make decisions, and then finding a home, it would be nice to be compensated because most of the work on my end is done at that point.