I was wondering how many miles a 1999 Jetta or Golf (new body style) will go and what kind of repairs they would require.

Ditto with KB. Make sure you keep up the maintenance on it and that car will last a very long time. However if its an automatic, there’s a good chance that will eventually start to give out since Volkswagen isn’t known for making the best automatic transmissions. A technical glitch isn’t out of the question but when they do happen they’re nothing major by any means. Otherwise you should be set to go! Hope that’s somewhat helpful!