Great advice, always a wise decision to save money as early as possible. Thus, one can collect an emergency fund, save for future investment, and prepare for unforeseen circumstances.
I think this is the main point, as a second backup through a side job, whether business or otherwise, at least provides additional financial security to achieve financial independence and achieve financial goals more quickly.
When I've asked financial advisors, they're always telling the same thing and that's to have an EF, yes emergency funds. And it's like having a 3-6 months of EF based from your monthly salary.
If one can have that and directs into investments, that's still a good strategy. IMHO, whatever works for your perfectly, you need to be consistent with that.
And if you're able to build your investments then it's time to have the EF focused until you match what's the recommended amount.
Emergency funds are important because you can never know what will happen so better if you have funds that you can use if you experience unexpected situations wherein, you need money for you able to overcome it. Majority of the normal persons, do not have it because they do not really know its real purpose and that is the reason why they are struggling especially when they face emergency situations. For me it is important and consider as necessity especially if you will also make an investment in crypto market.
You need it as a safety net that you can use if you experience huge setback or incur losses but make sure that your priority is a lot more towards investing and not savings. As for me, better to save your 15% of your monthly income, put the 45% of your income to investment and lastly put the 40% to your basic needs and necessity.