What SeDaTed said is true with the timetabling. I was really lucky and managed to get a pretty flexible timetable for my 17 hours so I could work on the off days, weekends and afternoons (I had something like 3hrs of spare daylight time a week
). But 17 hours and balancing two jobs that totalled to 26 hours a week was not good for my uni marks. 1HD, 4Ds, 3Cs and it was all really stressful just to get that. I wouldn't have done it if I didn't really REALLY need the money, and if you have any choice --- don't go along that path!
I only had 17 contact hours a week. A couple more and I think I would've collasped. It's not just the contact hours either, you have to take into account:
1. The group work where you have to have meetings and deadlines that you can't postpone because it affects the whole group. (Damn, responsibility sucks.)
2. Travel time. Even if your job is close to uni, it'll still take you time to commute. I found the 1.5hr trip from home to uni was so precious in terms of nap time because it was one long stretch from point A to B. But on 15 minute trips you can't nap particularly well.
3. Breaks between classes. Try as you might you can't be superman and zip from one side of USYD to the other in the 5 minutes between classes or surreptitiously eat under the table in lectures all year, so 1 or 2 hr breaks in your timetable are ideal for this reason. But on the flip side, it doesn't work too well when you want to fit in 20+ hours of work.
4. Social time. When your timetable is so packed it's hard to spontaneously go out with friends and it's likely their open times will not correspond with your 3hrs or whatever you have free a week. (Note to self: Will drop working hrs stop neglecting friends OR at least force them to make their timetable suit mine. Mwahaha.) And you miss all the TV that's on which sucks.
If I were you, I'd seriously ask myself whether I really really need the money and whether I could find someway else to do it. From your post I gather that the need for money isn't immediate, and you're just saving up for a few years down the track. Have you planned out how much you really need to be 'financially independent' as you say? Could you work less hours a week, say around 10 and still be able to afford living standards as current and be able to save enough come MBA or whatever?