Suraj let me just say that trying to build any CNC machine on the cheap never works.!! . . . . It always costs you more in the end.! . . .BUT . . . Trying to build one capable of cutting steel on the cheap is DOOMED from the beginning.

The best advice I can give you is STOP.!! . . . Don't do or buy anything as you simply haven't spent enough time doing the research that will be neccesary to achive building any CNC machine let alone one built on a budget for cutting hard materials. And I'm Not even meaning steel just the more dense Hardwoods or aluminium, Steel is a whole differant ball game which I suggest you forget for a first build.!

Go read most of the build logs to get some idea of just what's involved in building any machine. Read them properly not just flicking thru as you'll learn more that way.
Read every thing you can, then read some more and just when you think you have it sussed read it all again then come back with a design and we will start with the advise.
While doing this Save up your money and forget trying to build cheap it just never works out cheap in end.!