Always easier to pick up the extra unit and then drop it if you think it's too much than it is to start off with only 1 or 2 units and then wish you had of done the 2nd/3rd/4th ones as well. I started only doing 2 for my first year to get the hang of it and then went to 4, which is full time study. My uni has trimesters and I have been studying over those to do a 4 year degree in 3.5yrs so it's been a hard slog. when I started i still had two kids at home for a year, and my youngest started school this year. But then I also started part time work 4 days per week this year so it was a learning curve to get used to family/work/study and my marks did drop back a little which was hard for me - I'm also the type to doesn't settle for anything less than a distinction grade or higher. So if you are the type of person who would find that hard, at least you know that so you can work out how to manage your time to let you dedicate more time to getting it right so you don't get the low grades, kwim?