As others have said - an X5 is not an inexpesive vehicle. The cost of purchase is fairly low on a higher mileage example, but the reason for that is the high maint costs. Which is true of most all BMW's and really German sport / lux cars in general and is not limited by any means to the X5. It can be an excellent purchase at 20-50% of MSRP depending on age / mileage and they are fundamentally sound vehicles. But if you do not have the capability and time to perform the maint and some repairs, this may not be the best choice for you. The ML Benzes have an even worse track record.

If you are looking for AWD purely for snow driving, not off-roading, and you do not need to tow, I would suggest looking for an AWD wagon instead. I think the best one out there is the W210 E320 4MATIC, which has much more cargo space vs. the X5 and similar passenger space. These are very reliable vehicles and relatively simple to maintain, yet provide excellent luxury and build quality that you would expect in a premium german car that ran $50K+ new. They are priced quite attractively right now.

If you really need an SUV for towing or off-road capability (although seems you have the Bronco avail for that) - then you might be better off looking at a 4Runner. I have a buddy with a late 90's era example that has well over 200K miles and it has been very reliable. Hard to go wrong there in terms of cost of ownership since you are looking for something cheap.

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2003 4.6is - SOLD
2003 M5 Imola
2008 Mini Cooper S
2011 Mazda CX9