If I want to invest, I have to have a stable income system from which I can earn money on a regular weekly or monthly basis.
No you don't. If you want to invest in bitcoin all you need is to have income that is greater than your expenses. Now if you want to continue to buy beyond the first purchase and/or you want to hang onto your bitcoin and not end up spending it to cover your future expenses, then you have to have enough income or savings to be able to pay for your future expenses.
Keep in mind there is one point in time in which anyone might buy bitcoin and expect to be able to continue to hold the bitcoin and to buy more bitcoin in the future, yet the future is not completely known. Each of us might strive to keep our job or we might strive to control our expenses and/or to otherwise manage our cashflow with back up funds, but if we end up having future expenses that are greater than our income and we deplete our various forms of savings and/or back up funds, we may well end up having to spend our bitcoin at a time that is not completely of our own choosing.
Exactly... Some folks believe it's all about making that first Bitcoin purchase and subsequent purchases, but they often forget that it is also very crucial for them to place themselves in a financial position, where they can comfortably hold on to their stash without feeling any form of pressure. When an individual's income is greater than his expenses, the surplus, which is the discretionary income could be set aside for Bitcoin accumulation and that way, you could peaceful accumulate your Bitcoin with all your expenses completely covered thereby reducing or even eliminating any form of financial pressure.
Although, the real challenge isn't actually accumulating Bitcoin, the challenge comes right after that. Life like we already know isn't static and it's normal for things and situations to change. Such as job loss, unprecedented increase in expenses, emergencies popping up from the Blues and so on, and without a form of cushion or safety net to fall back on, you may be left with no option other than to dip into your investment at a time that you didn't initially plan to, which as we know could potentially undermine the whole purpose of long term Investing.
And this here is the main reason why cashflow management is essential for everyone who wishes to succeed as a Bitcoin investor. It's far from just earning enough, it's more about knowing how to structure your finances in a way that they'll be able to separate the things you actually need for survival from what you can actually put away to invest for the long term. And failure to do this may result to your Bitcoin becoming an alternative or substitute for an emergency fund, and all road may lead to selling off your Bitcoin prematurely. On the other hand, when you've build a solid buffer/cushion and all your expenses are well covered, it becomes a lot more easier to accumulate and HODL on to your stash for the long term without feeling any form of pressure or the urge to panic-sell when the market hits a potential downturn, and you can keep accumulating and stacking up those sats without worrying or having that fear that your future expenses might make you ruin your investment.