What is done about a person who leaves everything behind and disappears?

Say someone just gets fed up with everything, and one morning, they just walk down the street, and are never seen again. Friends, family or coworkers have no idea what happened.
Let’s assume that wherever they are, or that if they died, the person/body is never found. Obviously, they will be reported as missing. We’re talking about an everyday worker or family person, who probably has debts and things to pay. The authorities probably look for them, the government probably tries to get whatever the person owes, after some time, from someone related, like the family?

I’m thinking here, a homeless person who happens to be missing, no one will ever go to too much trouble looking for them, if any, and if anyone even knows they’re missing.

So, what happens to a person that has a normal life, and then just disappears? What exactly are the actions to be taken, and by who? How long do searches last until it’s given up? In addition, what does happen to a homeless person that is reported missing? (by either another homeless, or someone who knows them) Does anyone look for them?

I’m aware that a missing child is priority, but I’m looking for scenarios with people who contribute to society daily, or who don’t, but theoretically could, in ways kids can’t. What is done after a search is called off? (I know there’s limits to active missing people searches) Where does the government get all the money these people might owe?

Disclaimer; I’m not looking for advice on leaving it all behind. I’m just really curious as to what exactly happens, what steps are taken and all. I thought of this a few days back, when someone was talking to me about this movie, Falling Down. (which I’ve never seen)

and no I didn’t kill anyone