Generally speaking if you are dreaming of racing in a top series like v8 supercars and you aren't racing already you're two late. Getting a seat overnight doesn't happen. The typical path is from karting into, one of the feeder series and then to the big league. It doesn't happen overnight and it isn't easy you have to be good, very good. And frankly the odds that you are are low.
An alternative route for the late starter is to be a good driver and get into one of the 'one-make' paid and competitive entry series. Slipstream (dylan) from this forum was talking about trying this. He is a very good driver though.
And thats the pro stuff out of the way, take heart though there is alot of oppurtunity for amateur racing. Join a club (use google to find one) that suits your interests. There are lots of brand clubs that participate in motorkhanas, hill-climbs, track sprints, etc. There are also specialty clubs for racing types eg rally clubs, drift clubs, track clubs, etc. Join one that suits you and learn.
There is one final option. Race crewing. This gets you involved in pro racing. You can fill such roles as:
-Pit crew
-race engineer
-engine builder
-tuner
-suspension set-up
-aerodynamics
-etc etc.
All of these roles require either a degree in engineering (mechanical, electronic, aerodynamic, etc) or trade qualifications in areas like machining, mechanic, fitter and turner, boilermaker, etc etc.