In John Steinbeck's Of Mice and Men, Candy is isolated. This is due in part to the situation that exists for all of the men at the ranch. They, like many others, must travel across the country trying to find work in light of the Stock Market Crash of 1929, which started the Great Depression in the United States. They don't have a place to call home or their own.
The other reason is that Candy is disabled: missing a hand. As long as he can work, he will be allowed to stay. When he cannot stop his dog from being shot, it is clear to him that once he is too old, or has outlived his usefulness, he will be let go without a second thought.
As we read the story, we find out that the dream Lennie and George have really appeals to Candy as well. He has saved a large sum of money and offers to help buy the land so that they can all have a life of meaning; he, too, wants to stay in one place and harvest his own crops instead of doing it for someone else as he has done for so long.
Everybody wants a little bit of land, not much. Jus' som'thing' that was his. Something' he could live on and there couldn't nobody throw him off of it. I never had none. I planted crops for damn near ever'body in this state, but they wasn't my crops, and when I harvested 'em, it wasn't none of my harvest.
Working with the men on the ranch, Candy knows that he will not be able to stay there forever. One day he will be out of work, and with his disability, what will he do? So he puts in his lot with George and Lennie, pursuing the American dream of the 1930s.