Of course DCA can be done only if you have a steady source of income or money. I think the best time to do DCA is when the market is falling, because where you buy, if the price goes down from there, you have the opportunity to buy more.So along with money, a suitable market is also very important. Bitcoin price also plays a very important role in DCA
There is no denying that money is necessary to do DCA, whether you have a large amount or weekly or monthly it doesn't matter. You can take advantage of DCA only when you have the opportunity to make frequent purchases at lower prices.
Even if you don't have steady source of income you can still invest on Bitcoin using the DCA method, actually I know that steady source of income could also serve as a propelling factors that fuels the accumulating process of Bitcoin but however saying that DCA method is only meant for those that has a steady income will be indirectly saying that a less privilege cannot be able to accumulate Bitcoin, actually Bitcoin investment doesn't only give room for the rich but also to those who doesn't have much money to invest. So let's not miss Understood DCA method for a normal investment method were you will like to have enough funds and steady income before you could invest on Bitcoin but DCA method work contrary to that.
Well there is a certain presumption that a DCA approach is taking from either discretionary income (so that is income that is extra after any expenses that you have) or that it is being taken from some kind of a lump sum of savings - so it could be done in either scenario, yet I would think that drawing from discretionary income is the most wide-spread and applicable to the most number of normal people.
Normal people do not tend to have a lump sum of savings or other assets that they could draw upon in order to DCA--- so most likely the vast number of normal people are going to be weighing how much extra income that they have and that they are able to invest into BTC (or anything else) after they also figure out their expenses.. so then the investment amount comes from whatever amount of money is left over after accounting for expenses (which is also known as discretionary income).
If you do not have discretionary income, then you most likely should not be investing in bitcoin or anything else...
Of course, you also should have some kind of emergency fund that would be able to cover 3-6 months of expenses, but I am not opposed to multi-tasking that involves building up of the expenses stash while investing in bitcoin - however some people are in such bad financial circumstances, that they probably need to reduce some of their debt prior to investing.. so if they are paying high interest rates to service debt then they may be better off paying off some of the debt prior to investing into bitcoin or anything else.. yet I don't want to be a debbie downer, and there could be ways in which some folks could pay down their debt, build their emergency fund and also invest in bitcoin at the same time, but most likely that comes from discretionary income (which is the amount of income that is extra after paying for monthly expenses).