The "dream farm" is something we've heard George and Lennie speak of several times in the book by the time Candy becomes involved. Steinbeck creates excitement by bringing two parts of the story together about halfway through the story.
Up to this point, George has used the story to pacify Lennie, to make him feel better about how things will be one day when they have their own place. Then one day in the bunkhouse Candy overhears them talking about it. Unfortunately, Candy is suffering because his dog has just been shot by another ranch-hand, and he feels lonely and old.
Keep in mind that all three of these characters feel a kind of hopeless sadness about their future. They have no prospects for a better life. Lennie, with his child-like mind handles it better than the others and seems to actually believe it could come true.But George and Lenny have never been able to save any money, so they've never had the opportunity to buy a place.
When Candy overhears them he engages them in a discussion about it. Here's how they get excited: It turns out that Candy has several hundred dollars saved. Suddenly George realizes that this might be enough to buy a little place he has heard about. When Steinbeck has the character of Candy suddenly reveal that he has the money, George, for the first time, sees that the dream could become a reality. He takes he plan a few more steps and explains how they could buy the place and start living on their own land.
Then, once they realize that it could actually happen, Steinbeck spends a few pages letting his characters talk about the things they'll do on the land. For the first time, it seems real.
Unfortunately, a problem occurs almost immediately after this scene that throws everything into jeopardy.
Steinbeck creates a genuine feeling of excitement amongst these three people as previously in the book we have heard George and Lennie speak about this as their dream farm which George usually tells Lennie about to pacify him about how things will be one day. But when Candy overhears them speaking about this place he seems interested and wants to get involved as at this point in the book he is suffering because his dog has just been shot and he feels lonely and old.
This is when they get excited as they realize that with Candy’s saved up money they could have enough to buy this little place George has heard about, and their dream could become a reality.