OP, I've read your posts and it sounds like you're pretty amazing! Always worked, went back to study, raised a number of children and still have some at home and were able to be generous enough not to charge the older ones rent while they were at home. Honestly, on your own, that's pretty damn amazing.
I came from a similar home. We didn't have a lot, I can remember getting the odd food hamper from a church and how much that helped mum. She was also on her own, did cleaning and whatever unskilled jobs she could find to keep us afloat and buy a home eventually. I stayed at home during uni and she didn't charge me rent, I moved out at 22.
I've also worked hard, done pretty well. If mum was still here, she'd be proud. I've always worked full time, no paid maternity leave, so back to work when each of my kids was very little. We are definitely better off than mum was, our kids have had a pretty good life and we didn't charge them rent because we didn't need to.
Kids though, they sort of come to expect things that aren't always realistic. They want to be treated as 'grown up' but they are always happy for the bank of mum and dad to pay for outings. Now, we are in a position to do this, but I don't want them turning into ungrateful twats, so despite the fact that I could afford to pay, I don't always pay. When I do pay, I will sometimes message one in particular to remind them I'm not paying for the most expensive item on the menu. Even though we are lucky enough to afford to be generous, I don't want to be crazily wasteful either.
Ours have learnt from this. Sometimes we will get food and they get their own drinks and they will offer to grab us a drink too. If I'm going to lunch with one of them, I will probably pay 4 times out of 5, but sometimes as we sit down to order, I'll just tell them that lunch is on them today. I'm mindful of them in return, so I do this somewhere that I know also won't break the bank for them and I also don't order anything ridiculously expensive.
I like the idea that someone else shared, about going to a place with a bit of a fixed price option or a lunch special etc too.
It's easy for young people to be oblivious to the struggles of others, so they need to be reminded and taught to consider others. Even when you've nailed this as a parent, they can still forget that 'others' includes their own parents and our generosity shouldn't be taken for granted. Our generosity doesn't come with strings attached, but nobody likes to feel like they're being taken for granted, even if they can afford it.
As someone who has been through some very lean times, it feels good to be on the other side of that, but I haven't forgotten what it was like at times.
Keep going, you sound great! Hopefully the kids will all grown up and leave home eventually and the cost of living will ease for you too.