George's dream is to own a ranch with rabbits, cows, and lot of crops. He also wants fruits to can and sell since fruit is easy to can.
This affects his relationship with Lennie positively because they can worm together to achieve the dream. Lennie has the same dream of owning a ranch too with rabbits.
George thinks this dream is worth pursuing because he is living in horrible conditions and rough money income. Also, they wouldn't need to worry about their boss firing them or anything because they will be their own bosses.