As an elderly woman, Grandmother Majauszkiene has plenty of grim experience of life in the packing yards. She is a neighbor of Jurgis's family and a fellow Lithuanian, so of course they hang out together. At first, Jurgis's family thinks she's a bit of a sourpuss. However, Grandmother Majauszkiene is also the one who points out to them how they have been swindled into buying their home. She breaks it to them that they have to pay interest on top of their monthly payments, and that the company is hoping that they will default on their loans. The thing is, the company can make much more of a profit on these houses by collecting the down payments of poor families that can't afford to buy the house outright and then evicting these families as soon as they miss a monthly payment. Of course, they are doomed to miss a monthly payment because stuff happens – people get sick or laid off, and there is no way to avoid it. Once the Jurgis family hears Grandmother Majauszkiene's words of ruin, they realize how screwed they are. Over the course of Chapter 6, Grandmother Majauszkiene transforms Jurgis and the rest from happy homeowners to fearful home renters.
Grandmother Majauszkiene has seen generations of immigrants coming into the stockyards from different places, and a number of these families have owned Jurgis's home. These families have all been booted out of Jurgis's current home for missing one single payment to the renting agency. Grandmother Majauszkiene tells Jurgis and the rest about these families – their illnesses, their injuries, their bad luck. It's clear foreshadowing of what's going to happen to Jurgis and the rest. Grandmother Majauszkiene also hints at another lesson of the book, which is that you can't be a capitalist and have a happy family at the same time.
The reason that Grandmother Majauszkiene has been able to survive in Packingtown, where so many other immigrants haven't, is that she has one son and no other family members: "her son was a skilled man, who made as high as a hundred dollars a month, and as he had had sense enough not to marry, they had been able to pay for the house" (6.5). The important point in this sentence is that her son had had sense enough not to marry. Having dependents like a wife and children is what ties men to their dreary lives in Packingtown. The get-rich-quick-dog-eat-dog mentality of capitalism (again, according to Sinclair) means that you have a choice: you can either think mainly of yourself and stay financially secure, or you can try to support a group of people (like Jurgis) and find yourself ruined.