1. How big is your family? 4x4 is good if you have more kids or drive to beaches often, else 5 series would be fine. I always find 3 series to be too small for family unless you are a young couple.

2. Pre-owned from a private owner or pre-owned CPO purchased from BMW? Better if you purchase a new or a used car from BMW used car showroom. Yes, BMW maintenance is expensive but if you buy a new car or your car is under warranty then BMW takes care of all your maintenance and even wear and tear. Best part is that you don't need to pay anything for it!

I suggest that you buy a 2011 onwards 5 series or X5 and enjoy trouble free drive for several years.