many ways to go on this, go-karts and the equipment isn't very heavy or room consuming. i'd look at a toyhauler and a F350 supercab that you can drive back and forth to work, store etc. I suppose a big toyhauler and a good used class 8 truck with the sleeper re-configured for more seats would be in the same price range, but you may get a look or two rolling into a kart race with a class 8 truck.
I may seem like a broken record, but right now during the off season, in a recession, and guys losing sponsors, racingjunk.com is your best bang for the buck by a long shot. Even something fairly new is half price right now, and you cannot buy the parts for the prices those rigs are selling for.
2001 GMC 6500 Topkick, 22' box, dropped frame, designed to fit into a 9' garage door. 3126 CAT 6spd Man Lo-Pro 19.5's w/ 3.07 rear axle ratio