Contrary to the first answer I have never known someone that bought a Jetta that old and did not have a bunch of problems with it. If it was a very nice reliable car in great shape it would cost more than $3,500.
The Jetta will probably have the same amount of issues as the Ford and the Ford...
I dont know what state your in but every states lemon laws that I have seen require a MAJOR MECHANICAL flaw that the dealer has to attempt to fix at least once for the car to be returned and you to get your money back. Your roof leaking would definately not fall under that category. I would say...