Suraj, Forget R&P from a Car but what you could use and is the next best thing to ballscrews for efficiency are timing belts and pulleys. BUT again I can tell you from experience that by the time you have bought all the pulleys and idle gears etc then they don't work out much cheaper than ballscrews from china.

Completely Forget threaded Rod it's absolute waste of time.

If you try to do this on the cheap I promise you will regret it and the only useful thing to come from it will be the painful lesson that it can't be done cheaply.!! . . . . . Don't get me wrong I'm not trying to put you off building a CNC machine, Far from it, I'm trying to steer you away from taking the expensive cheap route.!! . . . . Seldome does it work out Ok and nearly all those that do succeed end up building another as the first has too many weak areas to be worth while upgrading.!