Edit: I agree it's somewhat ethically murky if the real estate developer, who also wants to buy the property, is funding the partner-who-wants-to-sell's lawsuit. However, I would expect that if that lawsuit is successful, the parties would be required to sell the property, but not necessarily to the real estate developer - rather, they would be required to put it on the market and fetch a fair market price like a normal real estate sale. I don't see why the other partner would be forced to accept less than the highest offer on the property, which might or might not be the developer.