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What can you sustain on your investment if you don't have stable income? Everything will fall apart if you encounter financial issues since you might think about selling your Bitcoin if you don't have any option left.
So much better to find ways to create stable source of income so that there would be no problem arise towards your investment. We are talking about long term here and for sure we don't want to fail just because of small reasons.
Would be good for people if they can make everything sustainable since they can increase their chance to succeed without getting bothered by any financial disturbance.
Wait a minute bro, I totally understand your concern but as @JayJuanGee said :
So, many times they are doing their best to maintain as much income as they can and as low expenses as they can in order to be able to invest into something like bitcoin.
This means that anyone who already has the intention to save in bitcoin and does not have a stable income, they will try to find other opportunities to get additional income. That way someone will never have a problem when they have urgent needs and still maintain their investment.
Like what I am doing now even though I have a permanent job and a stable salary, I am still trying to build a small business to be able to get additional income. And the profits from the business can be used to do DCA every week. So even though I have very urgent economic problems, I still have a salary from my job to cover those needs.
The method I am currently using can be used by beginners who do not yet have a stable income and in this way beginners do not need to worry about still being able to invest in bitcoin even in small amounts.

Intention is something that must be instilled in someone who wants to save in the form of Bitcoin, because intention will be their motivation when they do not have a steady income and will try and work hard to get it so that their intention comes true. And when they get it, they will definitely maintain it so that they can still buy Bitcoin when they have an income and hope to last a long time because having Bitcoin in the long term will produce good profits and that is what makes someone have intentions that motivate them. And I am also very motivated by Bitcoin because of the money profits that I have previously obtained and am motivated to get the next profit because the long term that I did before was not too long, but the previous incident motivated me to get the next profit which is much bigger than before and I believe that.
I also have a stable income, but I feel that it is not satisfying because besides buying Bitcoin routinely and consistently, we also need money to meet our needs without having to reduce it, and also need emergency funds and savings that I don't need to mention the purpose because I'm sure everyone already knows and is always in every comment. And that's all that makes me have to have additional income and I have mentioned it here and I have a grocery store business and sell other things so that all of that can be realized but I am grateful that all of that is very helpful and can fulfill everything but still I always think that there is still something lacking and still want more income because that is my motivation to have Bitcoin and want or have great hope that Bitcoin can make me live peacefully in old age in terms of finance and that's what I always think about and I believe Bitcoin can make that happen and whatever it is.