Thank you guys 
But having said that, you're very, very brave for considering that.
Haha thanks!
But what exactly did you mean by that? 
Would the workload be ridiculous or osmething?
Well, you've got roughly 4 weeks to cover 12 weeks of material. That would be the case for commerce subjects such as Business Finance and Finance 1. If it's a science subject like Engineering Maths, then that's going to be tough so it'll almost be a full time job. You'll be at uni for roughly 3-4 days a week. And God forbid any clashes if you do two summer subjects.
That's not to say that it's bad though. It is still sort of manageable because I know a person who did Finance 1 and Linear Algebra last year over summer and there's this guy I know who's doing Derivative Securities and Engineering Maths right now. The latter is not coping well though.
Oh I thought it was 6 weeks..
Well the plan was to take 'Brand Management' and 'Managing and Leading Organisations' over the summer break.. And if there were a potential clash, i would replace the second one with another commerce breath or something useful. Just praying for no clashes I guess..
My main reason was to do one summer to free up the breath that would otherwise add on to my sem 1, year 2: quantum mechanices, thermal/classical physics and real analysis.. Which would be quite demanding for me :s Really hate the high no. of second year hours.
But then i decided why not try to free up next sem too by adding on a second one. But I guess I'll have to consider it more.

Thank you!
Edit:
But just by looking at this year's summer timetable.. Clashes seem unavoidable. :s Guess I'll have to find out a bit more.
How were your friend's comments on their experience? :s
Was it overly demanding?