Bitcoin investment is something we should not be in a hurry to start if we don't have a source of income. If you use the available fund to start your bitcoin accumulation journey without any source of income, you will tamper with your bitcoin holdings to survive when the available fund has run out.
In as much as I would agree on what you said but I think with a proper planning someone that doesn't have source of income could actually start accumulating Bitcoin, however he could start by using the little money he has to start up a business and with time and consistent you will see that the business will start yielding a good profit for him to start the Bitcoin journey while his normal business will now serve him as his source of income and before he realized he has already become a Bitcoin holder, however in life most people are always afraid of trying because they are clouded by negative mindset that's why most people will always speculate about the price of Bitcoin to get to a particular level before they could start buying and sometimes they miss out the opportunities because they are always scared of what will become of there investment. So actually with a proper planning there is no limitation to what someone can achieve through Bitcoin investment in the future.
Just know that someone who doesn't have a source of income and starts accumulating Bitcoin will end up selling his Bitcoin holdings one day to survive because he or she does not have enough money to save an emergency fund that will take care of his financial needs. I see your suggestion of starting a business as a bad one because inflation has made the price of commodities very high, and such a person cannot afford the money to start up a business that will make him or her start getting a profit in the short term to start his bitcoin accumulation.