you probably have 7% interest or less on that 50G and it is a tax write off. Keep that payment. If you pay off the loan you'll just be 50G down without a tax write off. ;)
And if he HAS to buy a new car, he should be a used car. Cars are the world's worst investments. Why anyone would buy something worth 35K that was worth 15K less the minute they drive away is beyond me. ;)
And no, investment isn't for those that are completely financially stable, it's for everybody who wants to BE financially stable. Long view v. short view. ASk Nicolas Cage and Antoine Walker if they want a 'do over'. :)