Likely looking around 1500-3000$ a year in maintence and that's if it's been somewhat taken care of. Look for white or blue smoke on start up...
They all have waste gate rattle, even later models with the newer style turbos. They all rattle, guess what? N55s have started doing it too.
Besides the usual suspect oil leaks the early N54s weren't exactly stellar when new. I'd expect injectors with that low mileage. Intake valves will need to be cleaned, belt and tension replaced, vac lines replaced. Water pump. HPFP are so hit or miss, I know some cars that have had 3-4 done already and some that have had the recalled version installed ages ago and it's still okay. Being a 2007 it may not even have a factory oil cooler ... the CAS module will prob die soon...
not Horrible to work on no but when stuff goes wrong it's still not cheap to fix... I much rather go for an N52 , yes less power but less complexity. I'd pass on non LCI 335i
Don't boost it unless you wish to be replacing the engines ... We have been seeing more and more spun bearings on early cars and broken cranks. I
It's going to be an almost 12 year old car with service costs that have no really come down all that much since new. However there is enough information out there on what goes or how to fix it. I tell everyone but the best one you can with the best history but if it were me I'd pass unless the purchase price was so low you can have some play for repairs once you start driving it
