Wheel size education required

Hi all,

Could someone please educate me regarding the offset limits and rim width limits of the BMW E46 Non //M.

I am looking for a set of 18" CSL Reps for my 2001 BMW E46 330i.

Found these on Gumtree :

18" CSL Reps

They are a staggered setup with 8.5j up front, 9j at the back. The offset, front ET25, rear ET20.

From other posts and threads I have seen, the 18" is normally an easy fit, and the 8.5j and 9j don't seem to aggressive. The offset however, I'm not quite sure.

Any assistance would be much appreciated.