The old man of this quote refers to Candy, who is the first of the workers that George and Lennie meet as they enter the bunkhouse. What is key to realise is that in this chapter Candy tries to work out if George and Lennie can be trusted, and we witness a wary game as he reveals little bits of information about himself and the working environment they have entered until he finally gets George to make a "derogatory remark" about Curly, the boss's son, and thus feels that George can be trusted and opens up some more.
Note how this reveals that way that trust is absent so often between migrant workers. Not only are these individuals isolated, but also, when they do meet others like themselves the law of mistrust operates so much that they are very wary about each other. This quote is just another way in which Steinbeck presents us with a cruel, grim and bleak world where, for the majority of people, looking after yourself is the cardinal rule. George and Lennie's attempt to break the mould by travelling together and caring for each other is the main focus of the novel.