Too old to start racing?

Dont go karting at your age, go into racing. You may want to look into NASA (national auto sport association). It has given me very good experience since you go onto a track with a very competent instructor who teaches you the basics of high performance driving. After a few years you could probably start racing in the club and win prizes which would set you up for sponsorships and a racing future. Being able to race is not just experience however, it takes a lot of raw, natural talent as well. Hope you got some of that :)