English Idiom: On a shoestring
When a person does something on a shoestring, they do it with a tiny financial budget.
Think about the life of a college or university student. They have no steady job, not a lot of money in their pocket and lots of time spent studying. It’s a very frugal lifestyle.
There’s also a lot of Kraft dinner and instant noodles and maybe just enough money for rent and bus fare.
That is living on a shoestring.
Hopefully, after graduation, things get better, but nothing is guaranteed.
Unfortunately, many people manage to live on a shoestring for their entire lives.