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.
Please note this,There is no proper planning without a source, it is lack of orientation that makes most people think they can start a Bitcoin investment without a stable and passive income flow let alone other investment. However even if he uses the little money he has to start up a business after his initial purchase, what is the certainty that the business will yeild profit to enable him continue his accumulation, what if there was no profit out of the business he started, stable income flow is at top priority and highly esteemed in Bitcoin accumulation, similarly meeting up our basic needs and having a reserved and emergency funds are what will possibly help in achieving our goal, it is also advisable not to invest more than your capacity due to fomo, all these has been over emphasise in this thread, this is my opinion and view.