Over 15,000 in ten days?

If you have the highschool pack, you can sell outfits for crazy amounts of simoleons. Dragon fruit is expensive, also you could try getting a money tree. If you have horse pack, aged bottles of nectar sell for 2000 a bottle. You could try buying paintings from community spaces or art academy and then selling them on plopsy or buy from the flea market and then sell again with max prices. As last resort, searching for stuff in the dumpster usually gives expensive appliances and furniture you can fix and sell if you have the eco pack. The ray gun from science career can change items from a cheap one to a more expensive one, I forgot what the interaction is actually called but that's how one of my sims was able change her fridge. You could use that to change stuff and then sell it.

Here's a walk through of the scenario that might help.

https://simscommunity.info/2022/08/28/the-sims-4-scenarios-aliens-stole-my-parents/

I played that scenario and failed as well. I completed everything except the money. I played the Goth family, and Alexander aged up before they gained the money. It's cheaty but you can sell stuff from the house to make the money.

I think if either sim ages up before completing the scenario, you fail. As for rewards, I think you just get satisfaction points.

painting and looking for collectibles are some of the fastest ways to money in game i feel like

I often do those when my sims have mega bill to pay like by tomorrow and I'm missing some big money

Harvest all the plants at the romance festival. There are bird of paradise, dragon fruit and several others which will provide a good income when replanted on the home lot. I must confess to using them often to increase money - it's not really cheating! Good luck.

I'm attempting the "Aliens stole my parents" scenario. Incidentally it's a single parent who I am imagining is in prison for her criminal exploits rather than an abduction...

Anyhow. I have successfully raised the grades, group cooked and even completed the 'mind and body' aspiration with the child. Hiring a nanny will be no true hardship. I intend (if SimRealist's SNB mod will let me) to literally borrow the 15k in funds required (thinking of this as bail or a fine...)

Whether I cheat or mod the funds, the scenario did NOT recognize my legitimate completion of an aspiration that came after the scenario was programmed into the game. :/ So I need advice on how to cheat completion of an alternate aspiration or of the scenario's final requirement.

The child is a young male who is interested in science and has already got to level 8 of the mental skill. Perhaps unfortunately the family don't currently own a chess board... Open to options and opinions on which exact aspiration to tweak/cheat. ;)

Does the scenario require standard lifespan? If not, perhaps you could change the aging settings to give yourself more time?