Therefore, a long-term investor should first focus on emergency funds, keep a strong source of income as well as an emergency fund ready and continue to invest in Bitcoin for the long term, then good success will definitely come.
Having an emergency fund is important in bitcoin investment but not having it at first or not having a strong source of income as you said shouldn't stop you from not Investing in bitcoin or getting started with your bitcoin investment, for what you mostly need to get started is your discretionary income then along your investment journey you can now plan on how you can step up your emergency fund and also work on increasing your financial strength so you can keep your bitcoin investment going.
As waiting more further to have an emergency fund and also setting a strong source of income before getting started may lead to much delay and continuous procastination of not getting started at the end which you might regret why you never got started when the little opportunity was there to start accumulating Bitcoin.
The reason for the DCA strategy is to accumulate Bitcoin without first having huge income flow, buying gradually regularly and consistently either weekly or monthly and hodl for long.