finance at usyd is extremely mathematical/ quantitative (at least for finc 1). Without business studies/eco it will be harder, however, will just require more work, and might take you longer to understand concepts.
I guess another factor is whether you are able to sleep. For me, I had struggle sleeping till like 3am, because of stress or worrying about not getting sleep/ the usual insomnia cycle. However, fortunately, during the HSC exams I managed to get solid sleep. The odd night staying up till 2am...
With retail jobs, how much is the average earnings? Is it more suitable than tutoring (agency/ private) as there are chances of promotions early etc? Or would you recommend sticking with tuition, since it's lower hours, more than likely more pay as well.