for a start, parts affected by wear and tear, we cant escape the inevitably of changing them sooner or later.
Also, yes, unfortunately, bmw parts can be expensive, but not everything is.
Usually, the big ticket items are the gearbox, cooling system...etc. Basic servicing items are also pretty reasonably priced.
I think the main point is, if you plan to buy a car older than 7-8 years, let alone one that is almost 10-13 years old, there is always the likely possibility that major repairs are due sometime somewhere. Worst of all is, buying a car that is almost due for said "heavy repair", and owner decided to sell the car before it went kaboom.
2 ltr roadtax should be in the region of RM200-250 a year. i can't remember though. Fuel consumption and maintenance.. you could ask your dad about the E34 right?
but honestly, unless you have decent access to a lot of pocket money, I will recommend you stay away from an old beemer. But then again, what do I know, in my uni days, all I could afford was a bicycle 
anyways.. good luck in your car hunt.
