random question still deciding whether the costs of uni are worth it or not.

hey guys firstly, when do you start looking at 2nd year accommodation if your in first year; Is January usually when people do it and is it usually with your flatmates or coursemates.

Secondly, when it gets to 3rd year, do you stay in the same uni house as 2nd year; What happens if someone your housing with decides to do an internship or a year abroad and goes away , do you need to pick up what they contributed to the house each month and split it between the remaining flatmates if that makes any sense?

I am considering doing yr abroad but what happens when i return for my final year where will i stay?