Which is the best residential area near Macquarie University for a short stay?

There are lots of smaller residences (flats, townhouses) within walking distance in Marsfield, or cheaper places in Ryde (short bus trip). It is unlikely that there will be furnished ones though. The university itself has a lot of residential accommodation, you should check with them. They would most likely also be able to advise about furnished accommodation in the area.

In Australia, furnished apartments are at the high end of the rental scale. They are "holiday apartments" and tend to be more than $500 a week.

For a student I'd say Marsfield which is next to the uni.

Quest, Sheila has said exactly what I was going to tell you. If you check with student services, they have listings.

Epping or Chatswood.A 10mins bus or train ride to uni.