If you're physically capable of it and have time on your hands, helping the elderly can be one way to earn some money.
Highly depends on your skills and what you're willing to offer, but from my experience even just going grocery shopping for them or cleaning the house can be massive for them and based on agreements you'll get quite some cash. During covid I used to go grocery shopping for free for quite a few people and almost all of them wanted me to keep the rest.
(Example: I got 50€ to shop for items on a list, everything only costs 30€ and they let me keep the 20€)
I have seen people suceed in basically becoming someone's guardian and taking care of them (some with very low, and some with high efforts) and earning a lot, or being in their will after they pass.
But doing it for that little potential chance or actively looking for elderly without family would be way too cruel and undo all the good. But it's also pretty based on luck and other aspects.