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I agree with @sticky bomb, because someone may not have steady source of income but can have a discretionary income from his or her source of income. People with this mentality that someone need to have a steady source of income before the person can start investing in bitcoin are getting it wrongly, because what you need to start investing in bitcoin is you discretionary income , as in a left over money after you must have settled your needs and expenses either for week or for the month. If you can be able to make your discretionary income available from your main source of income then you can start investing in bitcoin with consistently with commitment and building up your emergency fund and your back up funds alongside your bitcoin investment.
In my opinion, this discretionary income can be used as your main budget source in starting investment and building your financial foundation, but you still have to find other sources of income instead of just relying on this one. You never know how much you can set aside each month which is then called discretionary, it also depends on how much your monthly income is and how much your monthly expenses are.
Discretionary income can be a source of backup budget in building a portfolio instead of spending it on frivolous things. However, do you really want to sacrifice many other things that you also need once in a while like vacations or other things because of focusing on investment?