You are misunderstanding the first thing that is needed before venturing into bitcoin investment which is an income and a discretionary income. I feel this is the primary thing because it's from your discretionary income that you will use to start your bitcoin investment and also for growing your bitcoin portfolio overtime with DCA buying strategy. It's also your discretionary income that you will use to build your emergency funds and that's why I feel that you can get started right away when you have your discretionary income and invest with one regular every week and use the other part to grow your emergency funds for at least three months.
If you don't have a discretionary income, and buy bitcoin with funds that is not your extra funds, you will end up selling your bitcoin quickly and I see that as gambling because you must get burned.
I do not consider the source of income merely as a primary factor for investment, but rather as the main or fundamental aspect of investment. If you seek investment advice from anyone, they will first advise you on having a prudent source of income or alternative income sources. If you do not have a prudent or alternative source of income, they will surely advise you to find a source of income before making any investment, and this source must be a prudent one. Alternatively, they might suggest that you combine a general income source with an alternative one to make it suitable for investment. Without an income source, investment is like a fish out of water—it will begin to die over time.
For those planning to invest, it is crucial to give the most attention to the fundamental factor of income sources. If you already have an income source, you must assess how suitable it is for investment, meaning you must have a reliable income source for investment. For instance, after fulfilling your daily needs, you should have surplus funds for investment, the income source should have a clear duration, and you should be capable of preparing a backup fund. If your income source is not prudent, you will need to look for alternative sources that can provide additional surplus funds.
By combining your primary and alternative income sources and ensuring that all rules and regulations for maintenance are followed, you can manage investments effectively. Only then will you be allowed to invest. There is no alternative to having an income source for investment. Ignoring this will make your investment unsustainable, just like a fish without water.