There are plenty of cars are sold by the members, as well some member are car dealers, look into it.
If you planning and willing to learn to maintain the car. You might want to look into buying Bentley manual, not the greatest by often better that nothing. OBD scanner also a great help.
The car can be driven in the winter, there are a few complication those. BMW sits relatively low. Most of the time you will be waiting for snow plow. Rear wheel drive takes a few empty parking lots to learn how to handle the beast. Also winter tires would be preferable. Although the body comes anti rust treated by the manufacture. Most often it is not enough so you will have to get respray once a season. That about of the top of my head.
Welcome. Will see you soon.