Driving a BMW isn't as expensive as most people think. Of course it can be more expensive if you compare with a Japanese car but not by much.
I think the most important think being a BMW owner is that you kinda have to be enthusiastic with car/automotive or with the brand, able to do research, know where to buy parts yourself and having some troubleshooting and diagnosis skill so you can tell what went wrong or at the very least able to determine the relevant components with your BMW.
If you are able to do your own research, then you will understand why most BMW enthusiasts never complaint much about their car being problematic (with a few exceptions like the SSG gearbox etc) because they know how to maintain and solve their problem without getting their throat cuts by the workshops out there. If you are the type that just want the brand but never intend to research, study and learn about your car, I suggest you to stay away from the car especially without warranty.
I am not very experienced with BMW but I just recently sold my Civic FD2 2008 and purchased a used 13 years old E46 330i, for the purpose of educating myself with a old and used continental vehicle. Also because the E46 is one of my dream car since young. And I can tell you the E46 is amazing even though it's decade old
To TS, if you like the F30 and must have it, then you must be prepared for the problematic encounter with the vehicle, but thus far F30 is a pretty solid car, there isn't much major problem with it. Go read on forums and you will understand more than opening a thread here. The 316i is by no means a bad car, it is good for what it is and for its value, test driven the car and I felt the car is more than adequate for normal driving and the 8AT gearbox is just amazing. I just didn't like the bench seats and the thin steering wheel. Otherwise, the car is good. You still get leather seats, xenon lights etc.
Personal advise though, I wouldn't touch a modern continental car without warranty.