The only thing that should qualify anyone to invest in Bitcoin is that the person must have figured out that he has a discretionary income, if not the person is more likely gambling rather than investing, our investment money should be a dependant of our discretionary income meaning that you are not investing with money that is meant to be use to sort out your other important needs.
There is no time of buying that is as perfect as as buying whenever you have your investment money readily available for investment and buy just right away, Bitcoin market is unpredictable and timing can be very complex and that is while the DCA strategy of accumulating Bitcoin solve this problem of timing the market because it allows investors to buy Bitcoin regardless of the price points, the essence of a consistent buying is to have a reasonable size of Bitcoin and hold for a long time 4 to 10 years or even more, so as an investor you buy at any market price points and not just to buy low and sell high.
Why do you say that you meet a requirement, will those who do not manage discretionary income not be eligible to invest in Bitcoin. I think you should honestly say that investing in bitcoin can be done if you have income.
As stated by JJG, discretionary income will never be stable, it can reach $100, $200 or $30 and it all depends on their living expenses.
Well, in investing if you buy regularly, be it $10, $20 and $100 per week, of course there is no problem, the important thing is to be consistent to increase your confidence in accumulating bitcoin.
Bitcoin has changed the views of investors or companies or countries because now companies continue to buy bitcoin and hold it.