I am also in an MSW program.
I have spoken with students that managed to work and do their internships (practicums) at the same time. The warning is: don't expect to do anything except work and school. Forget time with family, recreation, anything else. Also, you will probably have to have an internship based on what works around your work schedule, and not something you are necessarily interested in.
I am fortunate to have a job where I work 4 days/week. I am going to school part-time. My plan for my first practicum is to stretch it out over the spring and summer semesters (my school lets us do that), so I only have to do it 2 days/week. I am saving up all my PTO (paid time off) and will take an extra day off work each week during my internship. I won't have any classes I need to take during that time.
For my second internship, if I want to graduate in the spring semester, I will need to do 32 or so hours per week. My plan is to save up as much money as possible, and not work for that last semester.
If you want to go to school full time, that complicates things. Being part time, I will not have to take any classes during my practicum semesters. Frankly, I think going to school full time, doing your internships, and working would be close to impossible, unless you do well with no sleep. I need sleep. lol But I did meet a couple of students last year who did it. I think they did their internships doing graveyard shifts at city hospitals, and their jobs were flexible around their school and internship.
If you work at a social service-related agency, your employer might allow you to trade jobs with someone for your internship. If it involved learning new skills, it would count as your internship. I know people who have done this too.
My best advice is that if you need to continue working, go back to school part-time. It might take longer but I think it's the best way to preserve your sanity and get the most out of the experience. Also be sure to attend the open houses your schools of interest host, and talk to current students as well as professors. They can tell you how it's done.