You are absolutely correct, stable source of income is not a criteria someone ought to meet before they can invest in Bitcoin but it is good to have a stable source of income because if you are focused and determined to hold for long time, stable source of income will help you get there ( desire target) without much pressure because you will be able to allocate funds to different needs and wants and at same time grow your discretionary and emergency funds because these two are the ultimate for a healthy and smooth investment but regardless someone without this stable source of income can still do all these if they are very conscious about their investment and how to use their funds.
Well the both of you are misunderstanding what having a stable income can do for you when your investing. And you're also neglecting the fact that you cant keep up with your investment for a long term when you dont have a stable source of income. The reason why a stable source of income is important is not because of the investment alone, its because of the necessary things you must do before thinking about investment. I believe you know them. Without a stable source of income, you can't have an emergency fund, savings, and funds to care for your basic needs, talk more of to have discretionary income. It might make you want to tamper your investment.
I don't see why you are emphasizing more on a stable source of income instead of discretionary income for one to get started with his bitcoin investment. What will you say about those people who have a stable source of income without a discretionary income. Will those people be able to invest into bitcoin NO. Fine, stable source of income is needed to take care of your basic needs and monthly expenses but you need a discretionary income to use to set up your emergency funds and several backup funds. It's also your discretionary income that you need to invest in bitcoin.
However, a stable source of income that has a discretionary income is what can make us keeo our bitcoin investment ongoing for 4-10 years and above in order to build a good size of bitcoin stash. But it does not mean that if you don't have a stable source of income you should remain a no coiner when you have a discretionary income to put you in a low coiner level. This is why it's good that as you are investing into bitcoin, you should also be looking for other means to increase your income to improve your financial strength.