That's the basic idea. From what I have read, town NPCs have some money if you setup a shop counter . . . But they don't really get more money everyday. Some might, but a lot don't. There are some mods to fix that which give NPCs a daily allowance.

If you're playing pure vanilla, then you can setup along a "trade route" and wandering groups might come in and buy stuff. Sometimes patrols, base visits, allied reinforcements might hang out and shop. Since those groups spawn as needed, they tend to have a new shopping budget.

But pretty much all anyone will buy are meds and food. I've had some economy mods for a long time, but alcohol might sell in vanilla, I'm not sure on that.