contract law problem question

Legal Problem This scenario is based on an Australian contact law, please use relevant Australian case law and common law as references Sandy, who lives in Lismore, has a twin sister, Candy, living in Cape Town in South Africa. Sandy migrated to Australia in the 1990s and has always wanted her sister to join her family here. Sandy’s husband, Paul, is a renowned chef in the Northern Rivers region. They both own and run the successful Safari Fare restaurant in Lismore. They intended to open a second restaurant in Ballina and were in need of kitchen help. Believing that hiring family members was best, Paul persuaded Sandy to try to convince Candy’s family to migrate. Candy’s family has been running an eatery business and her two sons, Hans and Kane, are experienced in the food industry. Sandy told Candy that if she and her family were to move to Lismore, they could stay in the family’s self-contained unit on the same property rent-free until they found their own footing. Candy’s family could run the new Ballina restaurant and they could work out the terms on arrival. At Easter last year, Candy and her family decided that their sons would first make the move to try it out in Australia before she and her husband followed suit. Sandy and Paul have not been close to the boys, who last visited Australia more than a decade ago. However, having had several long telephone conversations with the boys, they viewed the boys’ arrival as a promising first step into enticing Candy and her husband to migrate. On their arrival last December, Hans and Kane were allowed to stay rent-free at the self-contained unit on the property with Sandy’s family. They helped to start the opening of the new restaurant in Ballina and worked there on agreed wages of $600 per week each. The boys proved to be naturally good at the restaurant business and the Ballina outlet became an instant success. Recently, Hans and Kane approached Sandy and Paul to buy over the Ballina outlet. They sat down together and drafted an agreement between themselves setting out all the terms but stated at the end of the document that it was ‘subject to the preparation of a formal contract by solicitors to be nominated by Sandy and Paul’. Last week, Sandy and Paul invited the boys for drinks to celebrate family success. An unfortunate turn of events occurred. Sandy and Paul and the boys had an intensely heated argument over politics. Their relationship irretrievably broke down. Angrily, Sandy and Paul told them to leave the self-contained unit within a week, and that they would no longer be supported in employment or business which included withdrawing the sale of the Ballina restaurant. Based on the above, advise Hans and Kane as to whether they have any enforceable contractual claim against Sandy and Paul. Your answer should only discuss the principles described in Topics 2-5, as relevant to the above facts.