I agree with the general consensus. Find a well sorted out car with lots of records and an anal owner....and don't be afraid to go across the country to find the right one (autotempest is great in this regard). Be persistent on making sure the wear and tear items are already done...cars, just like humans, go thru midlife crises between 70k-150k miles...ya want to make sure you find one that been to the right 'surgeon'. Might cost a bit more up front, but there will be fewer surprises. And it might take you 3-6 months...depends on how picky you are for the details (sport package, colors, etc).
Coming from the non-BMW world (Acura, VW, Subie) I think there are fewer dealbreakers (blown headgaskets, electrical nightmares, etc.)..but not putting off maintenance is key. I don't think the cars are ticking timebombs...remember folks who frequent forums are usually those who are passionate about their cars....I think you'll read more preventative maintenance kinda stuff here than you might on other car forums. Directionally the instance on maintenance is the correct things to do...but maybe not necessary RIGHT NOW, if you get my drift. But don't put it off entirely, cause you might pay for it big time (blown hg, rear subframe). BMW's are fun to drive for a reason..but those tight tolerances can be bad, as well as good. :-)
A local, trustworthy indie (and friends who are wrenchers) are essential to lower cost of ownership these puppies. If you haven't already, join your local BMWCCA chapter, you'll meet locals there who can help you (also, bimmerforums has a pretty strong regional section).
Finally, I would suggest getting a 330. I passed on a 3.0 in my z4, (2.5 instead) and I miss the extra 'kick'. However, given you are trying stretch the almighty dollar, I would not advocate getting a ZHP. They command a significant price premium ($1-$5k) for relatively little return on the engine investment....plus they are more likely to be beat upon than a regular 330.
"Don't be fooled, she drives with the aggression of a scorned 17 year old"
Last edited by TechieTechie; 08-18-2012 at 12:49 AM.