When writing an essay the you want to have a strong opening sentence and a good introduction. The second thing is to write strong supporting sentences explaining your choices and why you are taking the position you are taking. Finally you need a strong concluding sentence. This particular topic seems to call for more than one paragraph. It might be difficult to get the information asked for in one simple paragraph.
One important concept is to make the paragraph specific to you and give personal examples. A good introduction sentence might be:
"To live with someone, or alone, that is the question. I prefer living alone because the room can represent who I am. I can have a place to calm down without any interference. This is important when I have had a bad day. Another reason I enjoy my own room is because no one bothers my personal items. I remember last summer when I had to share my room with a visiting cousin and he lost several pieces of a puzzle I was working on. I will never enjoy sharing my room."
This is just an example but you can see the introduction, supporting sentences and a conclusion. Those are the most important items in writing a good position essay. The sentence in bold is your position, or thesis statement. After writing that you must give support for your position using specific examples. Finally summarize your paragraph.