It is not uncommon for people to say that without a good marriage Austen’s heroine’s face poverty. Tanya Gold said Austen herself lived in a “daily hell of boredom and semi-poverty”. Bidisha says Austen heroines live in the threat of poverty. Allison Juda says the Bennet girls “must marry well or face the terrible consequences of uncertain dependence for survival.” Professor Susan Zlotnick calls Pride and Prejudice a novel about “genteel female poverty”.
This is all wrong. What we are looking at are not the risks of starvation, but of leaving the gentry. The uncertainty is that of not being in the upper class, not that of survival. What can Professor Zlotnick mean by genteel poverty? The Bennet family income is in the top 1%! Sense and Sensibility might be about genteel poverty (though I don’t think so—they are far from Miss Bates!); Pride and Prejudice certainly is not.
If Lizzy Bennet remains single, then, after her father’s death, she will have about £40 or £50 a year, which was maybe twice the average income, and far less than she was living on as part of the £2,000 a year Bennet household. Branko Milanovic called it “measly”. But even if Lizzy is single, this is not starvation level, though it is less than Miss Bates’ income (perhaps £100 or £150).
But Lizzy almost certainly wouldn’t live on £40 a year. Put aside the fact that Jane will get married to someone suitable even if she doesn’t marry Mr. Bingley (one thing Mrs. Bennet gets right is that Janne cannot be that beautiful for nothing) and so Lizzy will always have somewhere to go,—Lizzy has her own prospects.
Lizzy is young, pretty, and full of wit and vivacity. She will surely be able to get married. She jokes that she will meet another Mr. Collins, but that is exactly what will happen. Her choices are not marriage or poverty. They are more like the choice between being Jane Bennet or being Charlotte Lucas. For an instance of this, we need only read the first page of Mansfield Park.
Remember, too, that Mr. Bennet is probably in his forties. He has another twenty years or so of life expectancy. At the end of the novel, four of his five daughters move out. Even if fewer of them leave, he can, presumably, finally start saving money as he ought to have done. He jokes that paying £100 a year for Lydia’s marriage will hardly cost him anything, compared to what she cost to keep at home, so let’s assume he can now save about £200 or 300 a year. If he does this for twenty years, he can leave Mrs. Bennet something like £4,000 or £6,0000, not so much less than the £7,000 Mrs. Dashwood inherits. Not enough for a cook, perhaps, but something.
Lizzy might marry an officer like Lydia (and be able to practice better economy), a clergyman (like Fanny Price), or a Navy Captain (like Ann Elliot). Even on a Captain’s half-pay (for times of non-commission), without Wentworth’s fortune, they would likely have an income of more than £200 a year between them. She will not, like Mrs Bennet, keep a cook, but nor will she be living in poverty.
Remember, on £500 a year, the Dashwoods keep three servants, and hope to save money. Mrs. Jennings thinks a couple can live on £300 a year. If Lizzy does marry a clergyman or an officer, he will likely have a small private income. Wickham was a profligate, who could have been richer. Lizzy would not marry so imprudently.
For Austen’s own Dashwood-like circumstances later in life, this is a very good summary from JASNA. Mrs. Austen and her two daughters lived on £460 a year at Chawton. (Jane invested her book earnings, £600, which gave her another £30 a year.) They had a servant and bought a piano. Austen travelled sometimes, went to the theatre, and went shopping. They were not in any sort of financial trouble. If three of the Bennet women had to live together, perhaps with supplementary income from their married sisters, they would likely be fine. There are risks, but not tremendous, unsolvable risks.
Perhaps, liker her aunt, Lizzy will marry a man in trade who has a very reasonable income—we are not told what, but he is believed by the Bennets to be able to muster ten thousand pounds to pay off Wickham. If she marries a professional, like a lawyer, she might even do almost as well as she did marrying Darcy—there were barristers in London who could earn £10,000 a year, though perhaps not every year.
The risk to Lizzy is staying single. What she faces then is a loss of control. She will become like Miss. Bates, or Fanny in an alternative life at Portsmouth. Austen herself was obliged to live with her father, and then her mother.
But the idea that Lizzy risks poverty is over-stated. What she really risks is living in a lower social class and living under the financial and social constraints of being a woman.
Real problems, but not as real as destitution.


Absolutely. There is "I've nothing to wear!" -and then there is nothing to wear.
I didn’t know Jane Austen invested almost 100% of her book-earnings in the Navy! But then, of course she did.