After deciding, in Chapter 41, that he can't accept any more money from Magwitch, Pip's assessment of his own prospects is rather bleak. He says that he has "been bred to no calling" and is "fit for nothing," except "to go for a soldier." The only positive prospect he has at this point is his friendship with Herbert.
Herbert suggests that Pip take a job in Clarricker's house, where Herbert works as a clerk. The irony here is that Herbert's wages, unbeknown to him, are paid by Magwitch.
At this point in the story Pip has become accustomed to the idle life of a gentleman with a benefactor. Without the money from Magwitch, Pip would quickly lose his status as a gentleman and descend back into poverty, and life for the poor in Victorian England offered very few prospects. Those without a job or a home would often end up in workhouses, which were not too dissimilar to prisons. Thankfully for Pip, he has a good friend in Herbert (and also in his brother-in-law, Joe, who he could ask for help) to ensure that the plight of the workhouse isn't his fate.