Most of the details in the description are found in Down and Out in Paris and London by George Orwell, though this is set in the late 1920s and not around the time of the Industrial Revolution.
“A down-on-his-luck journalist is the main character.”
The main character is Orwell himself, though he can only barely be descrbed as a journalist in the period when Down and Out is set. Later he wrote that “My literary efforts in the first year barely brought me in twenty pounds.”
When we registered [at the workhouse] I gave my trade as ‘journalist’. It was truer than ‘painter’, for I had sometimes earned money from newspaper articles, but it was a silly thing to say, being bound to lead to questions.
George Orwell (1933). Down and Out in Paris and London, chapter 35. London: Victor Gollancz.
“He has to sell his suit coat to a pawn shop to survive.”
I was left with only thirty centimes and no tobacco. For a day and a half I had nothing to eat or smoke, and then, too hungry to put it off any longer, I packed my remaining clothes into my suitcase and took them to the pawnshop. […] Seventy francs for ten pounds’ worth of clothes! But it was no use arguing; I had seen someone else attempt to argue, and the clerk had instantly refused the pledge. I took the money and the pawnticket and walked out.
Orwell, chapter 4.
Somewhat later (chapter 7) he has to pawn his overcoat too.
“He lives in extreme poverty for awhile.”
My money oozed away—to eight francs, to four francs, to one franc, to twenty-five centimes; and twenty-five centimes is useless, for it will buy nothing except a newspaper. We went several days on dry bread, and then I was two and a half days with nothing to eat whatever. This was an ugly experience. There are people who do fasting cures of three weeks or more, and they say that fasting is quite pleasant after the fourth day; I do not know, never having gone beyond the third day. Probably it seems different when one is doing it voluntarily and is not underfed at the start.
Orwell, chapter 7.
“I think he goes to a soup kitchen”
Orwell works as a plongeur (dish-washer and janitor) in restaurant kitchens (chapters 10–22) but possibly you remembered the descriptions of the Salvation Army shelter (chapter 29) or the workhouse (chapters 27–28 and 35).
“and sleeps in a poor house.”
At about a quarter to six the Irishman led me to the spike.† It was a grim, smoky yellow cube of brick, standing in a corner of the workhouse grounds. With its rows of tiny, barred windows, and a high wall and iron gates separating it from the road, it looked much like a prison. Already a long queue of ragged men had formed up, waiting for the gates to open.
Orwell, chapter 27.
† “spike, n. 4. slang. The workhouse. Also spec. the casual ward of a workhouse; an institution affording more or less temporary accommodation for homeless people.” (OED)
“He finally sells a story to the newspaper and makes some real money, getting back on his feet.”
A few days later I did receive exactly two hundred francs due to me for a newspaper article, and, though it hurt to do it, I at once paid every penny of it in rent. So, though I came near to starving in the following weeks, I was hardly ever without a roof.
Orwell, chapter 4.
This is quite early in the book, with many episodes to follow, so possibly you remembered that Orwell’s first big sale was the article ‘The Spike’ to Adelphi magazine in 1929.
“I suspect that the book was written by somebody alive during the time period it took place.”
The book is based loosely on Orwell’s own experiences in 1927–1929.
“The book took place in an English speaking country, probably England or the USA.”
Chapters 24–38 are set in England.
“I’m not sure, but I believe I read the book in school.”
This book (or extracts from it) are often assigned in schools.