Actually, a steady income is a MUST for saving a part of your salary in Bitcoin, especially if you employ a DCA sort of strategy. Because it doesn't matter what you call "prepared", if you don't have a steady income then you definitely ARE NOT ready.
U are right , before going into Bitcoin investment it is important one have a source of income , I have recognized the importance of steady income with my own investment journey , it is also good for long term investment success, when their is a stable financial income either with your job or other investment you can manage risk and it enable one be consistent in their investment.
Sure, once you lay your investment foundation very well at beginning of your investment, as an upcoming investors and you have all the knowledge of what it takes to be good investment and on how to go about believe me that you will make a good investors without considering the market price before you could go into investing, since we know that Bitcoin investments is what will take a longer time for you to have a reasonable profit you don't have to be in hurry but keep investment aggressively providing you have discretionary income at hands.