George and Lennie dream of saving up their money and purchasing their own small farm.
This is a part of the American Dream of land ownership that is largely out of the reach of migrant workers like George and Lennie. They crave it because it would give them a chance to put down roots and become part of a community, rather than wandering constantly in search of work. They dream of the independence it would give them, including the chance to take a day off if they felt like it. Further, rather than having to share a bunkhouse with strangers, some of whom can be unpleasant, they could surround themselves with friends.
Lennie dreams of raising rabbits, and George comforts him when they are both feeling down by conjuring an image of the bounty the farm would produce. This modest dream helps sustain them through the rough times they have faced in the Great Depression. Other ranch hands are also inspired by the dream and ask to be a part of it.