I don't spend much money on my "looks"
My main exercise is running and while I do a couple of classes, the same effect can be achieved with you tube videos and a couple of weights.
I've cut my own hair for years and it's a natural colour. There are a few silvery hairs, but they're still hiding.
I don't spend much on clothes and tend to go for simple styles that don't date heavily.
I have a decent diet, but more that I don't drink much, never smoked, and eat sensibly rather than eating lots of expensive "super foods".
While the stress and practicalities of poverty are deeply unhelpful, it doesn't take a lot of spare money to live healthily either.
I have good genes. My family tend to age well. Good skin (I also spend very little on skincare/ cosmetics), a helpful face shape. I'm a healthy weight and pear shaped so my top half looks slimmer which deceives people. My bust is faring well against gravity which is more luck than bras.
I agree that posture is important (I'm short and walk tall; the confusion upthread amused me!) I'm fit and walk quickly and energetically. If I go "oof" when I move, it's time to check my weight/ flexibility.
I think being IDed has passed by now, but I did accidentally get a child bus fare at 29 and gin confiscated at the till at 37. I'm probably looking more early 30s now, but a decade younger is fine by me. People look surprised when I mention having an 11 yo, and I was 30 when he was born so could have had him much younger!
Having enough money helps, but because I have decent health/ genes/ build, I can look after what I have fairly cheaply.