[ttldomination]

Well, as far as metal is considered, 1/8 aluminum tubing would be the lightest and kinda cheapest route.

Secondly motors, there are TONS available online. I would recommend he stick with the FRC stuff. Simply because all of the motor controller complications have already been reduced and it's a complete package.

I mean your choices are infinite. All he would need to do is type it up on google and find whatever he needs.

But personally, for an inexpensive project/build. I would recommend using either old parts, or VEX.