Go fishing, and sell the fish --- even if they're foul, have your Sims make something or write something, and sell it, or sell something else.
One time when my legacy family was new, I had them sell any expensive furniture that they had managed to afford, as well as extra lights in the house.
move/make more Sims into your household (There is a limit of 8 Sims per household.)
Have your Sims complete whims (3 thought bubbles above each of their heads) to earn satisfaction points. Once your Sims have enough satisfaction points, then, they can buy traits in the rewards store --- click on your Sims' aspiration icon in the lower right to see how many satisfaction points each of your Sims has or to enter the rewards store. Buy the frugal trait for 2,000 satisfaction points to reduce their bills each month)
https://www.thesims.com/news/whims-aspirations-goalsmore about whims and aspirations --- as well as a photo of what an aspiration icon looks like
Have your Sims always complete their daily work task at home. You can see that under their job panel at the bottom right. Make sure you send them to work in the right mood --- it will say that on their job panel, also. By doing those 2 things, your Sims will get promoted faster.
Also, if you have Get Together, then, you could create a club and invite Sims to do their daily work task as the club's activity. Buy the perk networking club for 500 perk points to get an even faster promotion.
Check the cost of items in your Sim's house. For example, my Sims can afford it, but they have a bed for §12,000, a bathtub for §12,000, a toilet for §1,800, and some fun activities for about §3,000 apiece.
or...if you really need to:
Press shift control c (all at the same time) to get the cheat console box to come up in the upper left hand corner, type testingcheats on (in the box,) and then, type money 22375 each time bills are delivered.
Then, after you pay the bills, type in the amount of money that your Sims would normally have --- So, money 500000 --- or whatever number.
Don't use commas when you type in the money amount.http://www.carls-sims-4-guide.com/forum/index.php?topic=23632.0.html#post_TChow to open the cheat console box --- or if you want to learn more about cheats.
