Living on a single source of income is not bad, but not totally valid, it also depends on how much income the person gets by the end of the month or week, if the income is very high enough to sustain every vital needs and still to invest then nothing much to worry about. But, owning a second part of earning is also a good move for anyone who would love to control more funds.
Relying on one income is not a safe idea. No matter the amount that the source is able to make for us in a month or year, it is better to have another source because nothing lasts forever and not just last alone. From time to time there is competition from others, and there will be advancement and development in all niches, businesses, or industries. If that source gets closed or is experiencing difficulty, then that is when our other business or work will help us maintain balance until we are back in track.
Don't forget responsibilities increases with time. You might be single today and in the next few years you might be married with kids and still have extended families to watch out for some time. Imagine investing $200 of Bitcoin and expenses cost you $300 when you are single at a monthly income of $600. And you choose not to diversify or extend your source of income. When you get a family or a bigger responsibility your expensive might increase to $400 to $500 and now you will only have about $100 or less to investing Bitcoin. his is why diversification and sorting for other source for more income is necessary.
Income and discretionary income are not the same thing, even though you might be describing something similar, but the concept of discretionary income is the amount of money that you have left after you account for your expenses. It is more accurate to say that we are ONLY investing from our discretionary income rather than just presuming that two people with the same income are the same or presuming that merely if someone makes more money or less money that he is able to invest in bitcoin or not. Sometimes people have discretionary expenses too, so if they cut some of their discretionary expenses, then they end up having greater discretionary income (more money available to buy bitcoin). Of course a person who chooses to spend 100% of his discretionary income on buying bitcoin is likely going to end up getting himself into trouble due to miscalculation of his expenses or even sometimes realizing that he needs or wants thing, so sometimes even within discretionary income there could be things that a guy wants to be able to buy from time to time or to prepare for some extra discretionary expenses through the month like going out to eat, drink or go to a movie. and so if he has spent all of his discretionary income on bitcoin, he might create some worse existence and stress for himself and perhaps even get into a position that he ends up having to draw from his bitcoin because he did not lessen his level of BTC buying aggressiveness.
Income and discretionary income can be very confusing to most people, especially to those who don't have a fixed salary coming at the end of the month. The concern is that if a person gets a monthly salary, it is easy to identify a discretionary income after removing the rest money for expenses in that month. But imagine a case where one has a skill and gets paid based on when he finishes his job, or the task given to him. This means at most it is difficult to completely manage and know what the overall income and the discretionary income are. Since his money can come anytime within the months and part by part based on the jobs and offers, he has that month. Such a person may find it hard to know the right percentage to use for the purchase of Bitcoin.
I see people in those positions when they calculate how much they made that month. For instance, it could be $2000 and what is left as discretionary income is $200. This is a huge issue for new or old investors. It is impulsive spending and improper records. For those persons who fall under this category, the need for becoming better should be put in place. Cutting down unnecessary spending and staying on a schedule will tend to harness the difficulties. I was concerned to talk about it because I have been in that position before and out of it, but many are still finding it hard to identify or differentiate possible income from discretionary income.