If you're looking for cheap motorsport come to Brazil and enter in the Peugeot rally cup. You pay about 50,000 reais which is around 18K, and for that you get a brand new rally spec Pug 207 from Peugeot Brasil, transport of the car to and from every race of the season, the subscription to the season, all the FIA approved gear, special discount on all parts (tyres included) and a few other bits and bobs I can't remember.
It works out cheaper than a season of karting, and it's of higher level.
My dad and I are seriosuly thinking about doing it in the nearby future, all depends if his new business goes well (Outlook looks good!).