In The Metamorphosis, how did the family survive financially when Gregor turned into an insect?
In the second chapter, Gregor learns that "in spite of all their misfortunes a bit of capital, a very little bit, certainly was still intact from the old days, which in the meantime had increased a little through the untouched interest." In other words, there was some money left over after his father's business failure, the failure that meant Gregor would have to work in order to pay off his father's debt. One might imagine that this money would be put toward Mr. Samsa's debt, but it was not.
Further, Gregor learns that the money he's been earning each month "had never been completely used up and had accumulated into a tidy principal." This is, of course, a surprise to Gregor because he assumed all of that money, except for the very few dollars he kept for himself, had been used to pay down the debt. Had it been used in this way, he would have been free of his horrible job sooner, but now, at least, he is glad that his father exercised such "forethought." It likely seems to the reader, however, that Mr. Samsa has taken advantage of his son.
In addition, Gregor's father, who had previously been almost a total invalid, has acquired a job—likely at a bank—and "hold[s] himself very erect," in his smart uniform, "the kind worn by messengers at banking concerns . . ." He now seems to take great pride in his position and also in his appearance, changing almost overnight into a totally different person. At night, Mr. Samsa falls asleep in his chair, and Gregor's "mother, bent low under the light, sew[ing] delicate lingerie for a clothing store; his sister, who had taken a job as a salesgirl, was learning shorthand and French in the evenings in order to attain a better position some time in the future." In other words, then, Gregor's family can, in fact, shift for themselves, and they do when it is required of them. They all procure jobs of one kind or another in order to avoid using up all of their savings.
Since Gregor can no longer communicate with his family, he is limited to listening to their conversations to find out what is happening. He was the major breadwinner, and now the family has no source of income. Gregor overhears them talking about their finances, and is happy to hear that they still have some money in the bank, as well as money that he had earned; despite their general ingratitude towards his hard labors, they have not spent all his money, so there is a safety net.
This money, however, was certainly not enough to enable the family to live off the interest; it was enough to maintain them for, perhaps, one or two years, no more.
(Kafka, The Metamorphosis, gutenberg.org)
Since this money is not enough to live on, the family decides to go to work. His sister takes a job in sales and his mother sews clothing and lingerie for a store. His father, who acts as an antagonist because of his harsh temper, goes to work as a bank messenger. Finally, because of their worsening finances, they rent out one of their rooms, and it is after all of these events that Gregor finally succumbs to the infection of the apple lodged in his back. The family then goes on vacation.