Never is a stretch. If you have NRaas SP, they can buy vehicles at the very least, and I get plenty of notifications like "Holly Alto's pockets may be empty, but her wallet isn't! Her household is now 3200 simoleons richer" and such. But even when they don't do that, I found that the net worth value displayed in MC is never equal to the lot value + household funds.

Love artist sims, mostly for the mood boost their paintings provide, and by extension an increase in lifetime happiness points.

"Her household is now 3200 simoleons richer"

Sims do progress in their careers, albeit at a much slower rate than if you are playing them; such notices are usually work bonuses. I've never known a sim to purchase anything autonomously ...perhaps if scripted? Probably a good thing, otherwise they would all own eight trampolines, five horseshoe courts, and would all die of malnutrition from eating nothing but snow cones (except for the ones who froze to death while playing in the sprinkler all night in mid-winter).

With Nraas' story progression money module you can have it set so inactive sims can purchase properties, cars, bikes, etc. when they get up enough money (luckily you can set a black list on what cars they aren't allowed to buy so everyone doesn't rush out to buy a cheap car) or automatically buy things like umbrellas and strollers. You can also have it set to move them to a more expensive house if their family funds gets higher than a percentage value of their house. It is set to have NPCs sell off things in their inventory, which tends to trigger when their family funds are low. (Story Progression is one of the mods Nraas' has that changes a lot of game code- it shuts off EA's progression and substitutes in its own. It also has separate modules you can add on to make it do additional things. It's a great mod but is a little hefty and has a lot of settings you can tweak.)

The 'Holly's pocket' notification is from story progression selling things from her inventory (likely a bunch of paintings since story progression also nudges inactives to practice skills related to their traits, jobs, or lifetime wishes).

Interesting. Thanks for the info; I was alluding to default sims' behaviour; with mods there are all sorts of unexpected activities.
I use SP but haven't done much tweaking (instructions are rather turgid), slowed progression slightly, removed some castes and jobs not relevant to my game, etc., otherwise let the town run itself. Have enough trouble taking care of my two sims in each world; they have full autonomy so it's often like herding cats.

Work bonuses? I don't know (I also don't own seasons) but this was in reference to Holly selling something, hence the "empty pockets". I have the job overhaul mod, so my sims have a 10% chance of promotion, and I decided to make it similarly hard for inactives to get promoted. And with SP you can even set minimum household funds to purchase a car for inactives so they can't just do it anytime they feel like it

Oh, I wasn't sure if it was inventory or something inside the house. And this triggers a lot in my game because of the high taxes I set, lol.