If you are having other sources of income then you can use that to pay back your loan, and the bitcoin which you are having in your wallet becomes your own, but most people investing in bitcoin do think bitcoin price will have increased before due date to pay back their loan, but things don’t really go like that.
Yeah , the profit shouldn't be the main dependant of payback, there could be even more opportunity to buy the DIP. I don't really buy the idea of taking a loan to invest in BTC , although there isn't anything wrong with it if there's always an assured means and source of paying back but with DCA I don't think worrying that much is really necessary and yeah it could depend on the intervals on how individual carry out their DCA, yet it is still possible to cover DIP with relatively smaller intervals such as a week.
Bitcoin, after declining from over $100k to the $90-93k range, provides a good example. Let's say an investor took out a loan to invest within that range, expecting a rapid price increase. Currently, they'd likely be focused solely on repaying the loan, missing a even more better opportunity to buying the dip. If they had used Dollar-Cost Averaging (DCA) instead, they could be taking advantage of the current opportunity to buy more Bitcoin, while also being debt-free. At the same time, it could workout for them but DCA doesn't fail by any chance.