This begs into question is it really all about the money? Sure we need to make it living and most of us want to make it to the big leagues and retire off of our passive income, but why hurt people just to get there?
I believe that, as a wholesaler, I am helping 3 people. I help the seller sell the house quickly and efficiently so that whatever tragedies that may be happening in their life, they can further reduce that stress. I help myself by feeding myself and my family as well as build up cash reserves. I help the buyer by expanding his portfolio and increasing the reach of his passive income goal. Sure the money can be even better if I squeezed the seller dry, but what kind of human being would that make me? I would rather only make $5k on a deal knowing that the seller is happy and the buyer is happy than make an extra $2k by hurting the seller.
So to answer the question: if they had an agreement they should stick by it, but at the same time I would let them know that hey if you don't get it sold by the end of the agreement, let me know and we may be able to work something out.
We all can achieve our dreams without sacrificing our integrity.
The people that are willing to step on others and trample on people to become filthy reach will definitely achieve their goals, but what happens when you change altitude too fast? You get dizzy and fall down.