Is there any idiom or expression in the English language that describes a situation in which the budget goes tight(er) and one becomes poor? In my mother tongue, they say "X happened and their bread gets thinner/smaller," implying on a situation in which the individuals should eat less as the result of economic hardship. Is there any phrase similar to this in the English language?
I've heard the expression "water down the soup", as in "The budget is pretty tight this week so we'd better water down the soup." It implies trying to stretch your resources. Adding more water to a pot of soup will get you more servings, although they will be less filling and nutritious. It's along the same lines as "spreading the butter thinner" mentioned above.
When I do a search on the web for this expression, all I get are links to cooking sites. However, there are various historical references to people watering down soup or making soup out of otherwise non-food ingredients in order to try to survive famine conditions, such as the French Army during Napoleon's retreat from Russia, so that might be a possible origin.
You can say they had to take their belt in a notch (or two)
From the Free Dictionary:
take (one's) belt in (a notch (or two))
To reduce, restrict, or limit one's budget or expenses; to live more modestly or make financialsacrifices. (Alluding to having a thinner waist line due to having less to eat.)
With your mother out of work, we're all going to have to take our belts in a notch or two for a little while.
The other commenter already mentioned the closely related 'tighten one's belt'.
"X happened and they found themselves unable to make ends meet."
make ends meet - To earn just enough money to pay one's bills.
- To make ends meet, Phil picked up a second job delivering pizzas.
- After the large income tax hike, many people suddenly found it difficult to make both ends meet.
- Since I lost my job, I’m finding it harder to make ends meet.
— Farlex via The Free Dictionary
If you say that someone has been put through the wringer /ˈrɪŋə(r)/ or has gone through the wringer, you mean that they have suffered a very difficult or unpleasant experience. It's possible that the experience is about great hardships and getting poorer. But the idiom in your mother tongue is still more specific, I think.
By the way, a wringer is a piece of equipment used for removing water from wet clothes by squeezing them between two rollers.
If you have to spend less money than you did before because you don't have as much money, you can say that you have to tighten your belt.
You can say "X happened and after that they had to pinch pennies".
A close parallel, the expression '[to] spread the butter [ever] more thinly is sometimes used. Though not easy to find in idiom dictionaries, an example from The Death of the Church and Spirituality Reborn ... Reverend John Littlewood:
The customary practice ... has been to ... spread the butter ever more thinly.
and one from Saxo Group tradingfloor.com:
Russia spreads the butter ever more thinly in 2016 _Nadia KazakovaNadia Kazakova
Russia oil and gas expert
Russia's budget for 2016 sees drastic real wage cuts for civil servants
Real wages already down 8.1% in 2015 / 2016 pay freezes set against likely inflation rate of 6.5%
Military spending cut slightly, but real pain among the population
Government effort to shore up social securities payments hints at cohesion fear ...
to get a shrinking slice or a thinner slice of the pie
This is an economics term. It is used all the time. It is not an obscure idiom.
Here is an example of its usage:
A Shrinking Slice of the American Economic Pie [title]
Workers are getting a thinner slice of the American economic pie even with strong growth, robust hiring, rising corporate profits and the Trump administration’s tax cuts.
Far more alarming, though, is the struggle over resources that is starting to take shape among the billionaires in Putin’s orbit. In January, I quoted Elena Panfilova, now the vice president of Transparency International, who predicted that the elites will start to cannibalize themselves as they fight over a rapidly shrinking economic pie.
Another phrase that might work is cut your cloth accordingly, which means that you have to make use of the (usually limited) resources you have.
- Peter lost his job, so his family had to cut their cloth accordingly.
N.B. This phrase is common in the UK, not sure about elsewhere.
Robbing Peter to pay Paul
Is an English idiom, it means, stealing money from one place, to pay it elsewhere, with the obvious effect of no real improvement in the situation.
The government, in taking tax on cigarettes, are ‘robbing Peter to pay Paul’ - when that money is later needed for healthcare costs.
When you take money out on your credit card to pay your basic needs, are you not ‘robbing Peter to pay Paul?’, he said.