Good advice, Fryke. And you have a good point, we are far too litigious. Legal action should be the last resort.
However, let me point out two things: First, if his mother is threatening to sell the car, arguably it is SHE who is threatening legal action, not him. He is seeking to prevent it.
Second: Yes, if his mother is ill, someone should try to help her. But please, don't ever think that absolutely ANY situation can be settled over a cup of cocoa with marshmallows. Anyone, saint or psycho, can have kids. Becoming a parent does not make you any wiser or more stable.
My wife has a friend whose mother is the most evil creature I have ever met. Forget taking her to a doctor: this woman actively seeks out doctors - and then she mentally assaults them, demanding drugs, treatments, and then becoming hostile and threatening when she doesn't get what she wants. Any doctor in the county runs screaming when they see her coming. The only way to deal with this woman is to stay far, far away from her.
I also knew a guy in high school whose parents were Christian fundamentalists, and from day one they drilled him mericlessly about heaven and hell and sin... Then one day they got divorced, VERY messily and acrimoniously. My friend ended up living with his dad, and a couple of weeks after Mom moved out for good, Dad's girlfriend moved in with them. To say this guy had some issues is putting it mildly.
I make my points somewhat flamboyantly, but I'm not trying to put anybody down: kanecorp, I hope you've made a real effort to make peace with your mother. But if you've done your best and you're at the end of your rope, there's no reason to sit still and take unlimited abuse just to avoid hurting her feelings.
On the other hand, if things HAVE gone that far, I definitely agree with the other posters here who say that you should be making real plans to move out as soon as you can.