I do think with a well thought out game plan and some fruggle shopping,you can build a respectable car on a reasonable budget. I do think you have to have patience though, as soon as you start seeing the light at the end of the tunnel on your build,it seems you just start ordering stuff. 
My original budget was 5k, the build came in at about 9k. Broke the trans., lost my brakes on the road course, then granaded the motor. Upgrade,upgrade,upgrade, now floating around 21k, Over quadrupled the original budget. But, it is a totally different car then I started with,handling ,stopping and power are greatly improved. When you stop upgrading the car its time to put a for sale sign in the window.  Ron
 
http://www.pro-touring.com/forum/showthread.php?t=38420
