You're doing your homework and that's smart! I was just kidding you a little
Common maintenance/repairs on boxsters:
RMS leaks (nothing you can do but inspect it and watch for drips).
Top problems with the original non-reinforced cables in the transmission. Not too expensive if you replace the cables right away, big bucks if you don't and it twists up your clamshell and top.
Plastic rear window can crack if raised/lowered when it's cold ($$$).
Coolant tank resovoir cracks with age and should be replaced if the car is 6 years old or older as a preventative maintenance item ($$$).
Car eats tires. No way around it with the camber and the hard driving you will do ($$$).
MAF sensors and O2 sensors can go out on older ones and they're not cheap ($$$).
Horn pressure plate (behind airbag) on the 4 spoke wheels wear out prematurely ($$).
Hinge on center console cover is crap. It will break and should be replaced with the new all-metal version ($).
Anyone want to add to this list?
Read the links in my signature line for other stuff to look for when buying a used boxster. I learned the hard way so it's experience talking.