yearly maintenance question....

[AtoB]

so, have 10 months to go until i need to buy a new car. currently i have a BMW M Z4. absolutely love the car, but 36 month is the longest i keep them. the two cars i am considering are a 2006-2007 Carrera S cabriolet or a 2009 Boxster S. i have driven both, the boxster definitely did not feel as raw as my M, but i expected that from all i have read. still a very enjoyable car.... and with an aftermarket exhaust, i'm sure i would be happy. the carrera S i drove was a 2006. there wasn't much lacking for me there. acceleration was great, handled and rode wonderfully. well, today i took my M in for service and bumped into my sales guy, who asked me... "so, you looking at a 911?"...funny, he saw me drive by him when i was testing out the carrera. i told him "yes".. that much as i loved my BMW, and i have had 4, the BMW really had nothing that interested me. the new Z4 is too soft, and the M3 cab is too heavy and big. so i know this is a long path to my question but, he shared with me that regular maintenance is not covered like with BMW.... wipers, brakes, oil changes. and to expect to spend a decent amount each year. honestly, i would rather drive a car that i am passionate about and pay for its maintenance than settle for something less than with full coverage. i know the carrera and boxster are different cars, but i'm guessing the oil changes, andd regular maintenance aren't too far apart cost wise. so, what should i expect on a yearly basis? TIA