I went through as a wife and mother of two. My husband worked nights. So basically I have no idea of what it's like as a single parent, but I do have an idea as a parent.
The first two years of school you are basically days and many schools have taped, videostreamed, or audio recordings with ppts online. Some students don't go to school at all and choose to just stay home and read. Be sure you look into schools you apply to however, as some have attendance policies. You have summers and weekends off. After second year you have boards in the summer, which will chew up a bit of your time, but after that you have off until rotations start.
Third and fourth year will be more challenging, but your child will be older too. You will have some nights, some very long hours, etc. But you also generally have holidays off. You will need significant help here with your child.
Depending on what specialty you choose to pursue, you may or may not have a whole lot of time in residency. Certainly no matter what, some rotations will be time intensive - 80 hours a week or so. Some will be lighter, around 50-60 hours. But you will have studying in there besides those hours as well. You can NOT count on nights, weekends, or holidays off. Ever. And you will never have a summer off again ever.
It's tough as a single parent. You will need good support structure and help with your child. But as a mother of children myself going through school, medical school, and residency, you will see them. Perhaps not as often as you would like, but if you ask my kids they are very proud of their mother. They realize hard work pays off. And we have a wonderful relationship (yes, we even made it through the horrible 12-14 years with my daughter. Fortunately my son is coming out of those years now).
Is it worth it? Only you can say.