How the girls make their own money in Bikini Bottom
Sometimes when they visit Bikini Bottom and they wanna buy things there, the girls take up being freelancers so they take up doing temporary and occasional short term jobs so they can get paid and make their money instead of relying on someone like Spongebob to give some to them.
When they temporarily work at the Krusty Krab, it's more for performing and singing for an occasional special event or party and when they DO get paid after it's over, Krabs gave them some type of pay but it's always minimum, but that's okay, they get extra money tips from their audiences too.
They take up babysitting for some kids for a few hours when they're parents go away to dinner for the night and even though the kids might be a hand full, their parents always offer great money so to them, it's worth it.
Another job they once took up is singing at a kid's birthday party as special guests that took place in Goofy Goober's Ice Cream Party Boat. Not gonna lie, they enjoyed it alot, especially Cat.
Another job they'll do is taking care of the elderly for the afternoon, they do get a decent amount of pay so they can't complain right there.
And finally one of their favorite short term jobs they like to do is taking care and cleaning the houses of the wealthy. Some of them were kind and some were rude, but they paid them great amounts of money, so it didn't really matter. However, their worst experience at that was doing a job for Squilliam who offered to hired them as waiters at one of his special event parties and while it went pretty well at first, the girls had no idea that those people were talking bad about them behind their backs while being "nice and polite" to their faces, sometimes they even threw them back handed compliments.
They were also made to do foolish acts but it wasn't to impress everyone or for extra money, it was to humiliate them in front of his rich buddies for giggles and their own amusement. Although Squilliam did actually end up giving them great amounts of cash in the end, both girls tell him they will never work for him again and Cat tells him how mean he is but Squilliam laughs and says "it was nice to have you girls here", not caring that he basically embarrassed the girls that night.
Overall, the girls don't always have perfect and great experiences doing short term work in Bikini Bottom but they always remember to appreciate the good experiences.