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.
Build a business first, get the profits, then invest in bitcoin?
If that's what you mean, can the business promise profits? I think every business that is built certainly does not guarantee that the entrepreneur will get the profit as expected, that is a risk that really should not be ignored. But your suggestion about how someone can have a source of income is correct, I also agree with it.
Business and investment both have risks, but the risks may be different. Investing in bitcoin is simple if you are only interested in being a holder, it can save more emotions due to uncertain market volatility. A person can invest in bitcoin even if they don't have a steady source of income, but they should at least have a way to save money whenever they have money. Despite their excessive fear of investment risks, they have never been forced to do so. Only people who can consider high risks are worth investing in, if they are afraid of losing, then they should just keep their money under a pillow.