Hi, I'm trying to figure out if I've done something wrong with my StoryProgression along the way, or whether this is normal game behavior. So I've started a new household in an existing world of mine, and I decided to make them a firewoman. I didn't have a existing firehouse in my world, so I placed one in. However, when my Sim started work, I noticed that there weren't any other firefighters in the world, and what's more, the only opportunity I got was from my one other inactive household. So I was wondering, is this normal? Do I have to manually place townies throughout the world to populate it. Or have I done something wrong with StoryProgression along the way?
Any help is greatly appreciated!

When you say this is an existing world, do you mean you've played this particular save before? Were there other residents that have since disappeared, or was the world always almost empty?

With SP, you can set up Rapid Immigration to fill the town with however many households you want.

SP > General Options > Options: Lots > Options: Immigration/Emigration > Rapid Immigration > [number of households]

This option is hidden when the Immigration Gauge is zero (in the same location in the menu), so set this to a nonzero number first if necessary. You can also play with SP's immigration options in that menu, for example adjusting the chance of SP immigrating a family vs. a single sim or choosing where the genetics should come from. With only two households in town, you may want to just use bin offspring, rather than the existing town genetics, and perhaps seed the bin with a variety of sims for SP to choose from.

However, if your save used to have more sims in it and they've disappeared, or this world is supposed to have an existing population, that's the more pressing issue.

Nah, it's a newish save, and I don't remember seeing other Sims when playing the previous household, so I'll mess around with immigration settings, thanks for the help!