I think that's partly why stuff like frozen pizza is kind of a meme with single people. Stuff in the freezer can generally keep for years before it really has anything off with it, and even after it starts getting a bit off, it's probably still not going to kill you.

Frozen pizzas can be had for as low as like $3.50 if you get them on sale, and since they keep forever in the freezer there's no reason not to stock up at that point...

I lived not-quite-exclusively on frozen pizza when I lived alone for about a year. It wasn't healthy for me, but it was pretty cheap living, at least in the short term.

Most fresh ingredients last at least a week. What kind of salads are you making that a single person can't finish before they go off?

I was out a lot anyway - lunch with work, dinner with friends, weekend catchups with family and so on. When you live alone, you need to leave the house to socialise. I was only home for meals a few times a week. And I didn’t want salad every time I made food for myself.

So yeah, usually I’d buy salad ingredients, make one salad (or veggie sandwich or something). Then a week later I would take a look in the fridge and notice my ingredients had gone bad. I did this several times before I gave up.