You are due to move into a rented apartment next month but you will not be able to because you have some problems.
Write a letter to the course provider. In your letter,
explain your situation
describe your problems
tell him/her when you think you can move in
I am writing to update about my delay in joining the course, as against the existing plan. I was planning to move into the rented apartment early next month in time to begin classes, however, unfortunately my family is dealing with some personal and unavoidable circumstances, due to which I am unable to do so.
My family is going through a tough time as my grandfather recently fell down and is hospitalised. At such difficult times, it is quite unsettling for everyone to leave each other. Additionally, I am aware that my course is about to begin and there are some decisions that need to be made by me, prior to joining the course such as accommodation, food, and my study materials. I am trying to stay connected with my batchmates as well as take care of family at this juncture.
Nevertheless, I would be able to join the course from the last week of next month and would be relocating into the apartment one or two days prior to that.
I look forward to your understanding and support in my difficult times.