[Myron Piatek]

Buy a competitive car from a reputable owner who has raced it recently and can demonstrate it. It would help if it's in an uncrowded class so you don't have to worry so much about getting beat heads-up and being tempted into "keeping up with the Jones' ". It's basically a dial-in bracket race unless you have a heads-up run. But it is important to be capable of running under the index under the worst weather conditions. (LNorton has similar advice on another thread.)
Building from scratch, learning and trying to stay ahead in your specific class is where it gets much more expensive. Just remember that eventually you will need the cash to rebuild the engine, converter and trans and need someone "in the know" to do it right.

Local bracket racing experience is important to hone your driving skills before investing in class racing.