Asides the DCA, Bitcoin investment is for those with a steady paying job, not for people that wants to risk their cash to make quick money, someone without a job can't even hold for long cause they'll be forced to sell during time of emergencies, their only hope would be one their investment since they don't got other money therefore it's not advised and whether DCA or not an investor should have a job already.
There are many people who do not have a monthly salary. But they have a stable source of income, they can invest using the DCA method.
Many people have a daily source of income, they can buy Bitcoin using the DCA method. Whether you have a monthly salary or a weekly salary, you can buy Bitcoin using the DCA method if you have a stable source of income. Because if you do not have a stable source of income, you may not be able to buy Bitcoin consistently.
As soon as you invest, you need to create a reserve fund and an emergency fund. So that when an unexpected disaster happens to you, you do not have to sell your saved Bitcoin. Always try to keep 3 times your stable income in the emergency fund and reserve fund.