I don’t know if I understand the meaning of the word “pension” correctly as the OP describes it. But if we talk about pensions, then, as far as I know from my country, they should always be paid for by the state. The amount of payments depends on the length of service the person has worked.
Is it possible to simply retire, in the OP’s understanding? Maybe it’s worth just reformulating the meaning that the OP wants to stop working for “uncle” early, that is, for the state, and become a free entrepreneur, free from the constant obligations of going to work. Then you need to take into account that you should not expect privileges from the state.
If you have capital, this is possible, especially if there is alternative, or better yet, passive, income.
But don't call free enterprise, or the free decision not to work, a pension.
Usually the word retirement is categorized as those who work for the government and companies. If the meaning is like that then someone can choose a period of service of more than twenty years to get severance pay or pension funds or by reviewing the rules agreed with the employer. But for entrepreneurs, it seems like there is no such thing as retirement, they will continue to run or be involved in their business even when they are old. For some people who are still provided with good health and mental health, it is unlikely that they will apply for retirement unless they choose to resign and return to work in another field. Of course there are many things to consider if someone chooses to retire from a job, inflation rates, taxes and other unexpected costs.