Under the Mattress It Goes
So you might not know this, but SNB was entirely created based off of my obsession of YNAB (You Need A Budget). I use it daily to monitor the budgets of THREE different households (again, because I'm obsessed with knocking out debt and saving a little here and there for future purchases/goals). I've even created Play Budgets because I'm that much of a Money Nerd. The urge to have this in my game had me reaching out to someone with more experience in coding to produce such an addition because I couldn't wait that long for me to figure it out (I can be a little impatient from some things ;-) )
October is the month of National Financial Planning in the U.S., and the re-release of SNB would've been a sort of celebration of this since you are essentially starting to make a financial plan for your Sim's Simoleons. Like for instance, creating a separate account for your Sim's Teen's Future Move-Out so you can turn their room into a Home Theater, Gym or Art Studio faster. Or putting aside some money to open a business or save for early retirement to go camp, fish, travel, or whatever your Sim desires!
However, since SNB is not available for public use at the moment (we are awaiting the November Patch and the resolution of an error we found), the only way you can honestly do something like this would be to put it under the mattress so to speak. You can do this by averaging out the Household's expenses to have a set amount needed on hand for at least four Sim weeks (or two weeks if your Sim has a shorter lifespan). Once you've got your 'emergency cushion' you can now add in how much you need to accomplish your Sim's goals (buy a better house, redo that dated kitchen, retire early. etc.). You will find yourself being super aware of what your Sim buys. Weighing out the pros and cons of that fully-loaded TV over a small update in the one bathroom your Sim has and needs to expand to better serve a growing family.
If you keep that small tidbit in mind, you can better accomplish all that your Sim would like to achieve in their very short lifespan. And if you need inspiration of what to pursue, just take a look at their Aspirations and Whims. Whims are more of short-term happiness to me. Aspirations are your Sim's ultimate goal or purpose in life. You can give your Sim a couple of Whims that affect your Sim's pocketbook but don't lose sight of their Aspirations. Ask yourself when you buy that awesome bar for your Sim, are you really doing it for yourself (so you can watch them party with their friends until the Sun rises the next day since you kind of can't with work the next day)? Or because your Sim loves Mixology and would like to be able to make a living off of that skill instead of being locked into a 9-5 job?
So take on the challenge of getting your Sim Financially Responsible and achieve Aspirations early! Gear all their financial decisions to their sole purpose, or drive in life. You will find the whole experience a lot more rewarding than doing whatever you please for a change.
Disclaimer: I do not in any capacity believe I'm an expert on this matter nor even in real life Financial Planning. This is more of my opinion or suggestion on the subject. You can take this as you will.