MDF parts required.

[JAZZCNC]

I wanted to use MDF as my first machine so that I can learn about the design and once I am not a newbie then I could use the knowledge gained from the this MDF machine to build a more permanent machine. Thus I am not intending on spending a lot as the machine will just be temporary.

Biggest thing you'll learn from this route is how to waste money.!! . . . . . My advise is read every build thread and soak up information and while doing this save up your money and build from correct materials and components from the start.
By the time you have the money together you should have a very good idea of what's required to build a good machine.
The fact you have no workshop facilities makes things harder but not impossible just more expensive.

PS how do you support the rails at middle ?

Use Supported rails which are supported across there full length unlike the unsupported type like your intending which are only supported at each end.!!