Back in the day that was the early 80s, I was poor, living on about $500 a month, 3/5 of which went to rent. I ate some cheap stuff. Most of that is forgotten, like Hamburger Helper without hamburger, but there are still a few things I eat on occasion from those days. So, what's your favorite poverty dish? I think mine is a can of green peas with a slice or two of cheese and seasoned with pepper and a few bacon bits if you have them. Another is a bagel with cream cheese and some pepperoncini to cover the vegetable angle. Then there's always spaghetti with non-meat sauce or just butter and toasted bread buttered and seasoned with garlic salt for that downhome Italian feast. And of course, spicy ramen.
In grad school I figured out that Top Ramen was cheaper by weight than rice. As such I figured out a bunch of ways to cook ramen including pan frying it.
Beans and rice with hot sauce and fried bologna sandwich with cheese if there was any in the fridge. Grits for breakfast...
In college, my go-to "good" "home-cooked" "meal" was mac and cheese with tuna stirred in. That's what I had for dinner at least 3 times a week. My go-to lunch while at work was going to the dollar store and getting those tuna + crackers combo things. Obviously, I made frequent use of breath mints.
Cans of tuna. Lived on that stuff. Fry it... make tuna salad... eat it with crackers... eat it straight from the can. Of course, you used to be able to get tuna for $0.50 a can a few years ago, so it was cheeper. Timmy Chan's fried rice back in the 90's was the bomb. You can order one and it could feed you for 2 or 3 days (not that I ever let it last that long). Nowadays cheap Chinese food places have gone the way of the dodo and you can probably make it yourself for a lot cheaper. As an adult... lentil/split pea soups (whatever variety), or other variety of soups. Canned soups are cheap, but you'll probably end up killing yourself on the sodium. lol. Another option is red beans and rice. You may have to forego the meat (or most of it) if you're really trying to be cheap. The best thing about things like dried beans, lentils, and similar items is you can buy a crap ton of them and just leave them in the pantry for whenever. They last for a while. That's why dry beans, lentils, etc. are usually my favorite choice for eating cheap. Grilled cheese sammiches, pb&j sammiches, spaghetti, etc. are all great for eating cheap, too, but if you're trying to watch your health while eating cheap, things become difficult sometimes.
Been on a black beans and rice kick lately. Poor people can be tough and rubbery, so 8hours in the crockpot on low. Good eating.