Every man on earth has her own set goals and a timee frame they're working with, financial stability age depends on your own personal goal but for me the earlier the age, the better because if the time frame set only gives room for less chance of maximization and expansion, then it is a wrong decision.
Early age of financial stability helps one to discover more hidden abilities and even go extra mile in doing more exploit, yes there'll be lots of years ahead to live and as these years pass, so does living and everything in it gets tough and cost effective more, we need to always blend in too every new cost development in order not to be caught struggling while pushing through life.
The 20's of a man should be a period of breaking bounds and making waves, laying solid foundations and building strong bedrocks to make room for better feats and reduce the struggle in his 30's.
It takes a set goal, determination, years of hard work to be stable, so it's really best the struggle to financial stability begins now to avoid pitiful circumstances
That's a great idea ! I really wish you could do it, but... as always there are nuances

If we are talking about the average citizen of the country, it is very rare to build a business at 20 years old. No, perhaps a person is a genius, for example, developed a new technology - he will quickly make money. Note that I did not say "build a business" or "ensure financial stability".
To build a business and create "stability" - you need knowledge, experience, understanding of the market, including the financial market. And here the age of "20 years" does not look the best.... Most likely, 99.9 percent of the population at the age of 20 will not have what I have described. At this age, almost everyone does not yet understand what money is, how to handle it, what is value and what is "empty goals"....
Even though I bought my first apartment at the age of 25+, it wasn't "financial stability", it was just "good fortune". And only after at the age of 35 years I started to form, consciously (though not without mistakes), something that can be called "the basis of financial stability"