Don't need to use a grey card if you shoot RAW - as you can adjust white balance to the temperature of the light in camera raw. Sure, it takes longer than doing a custom WB (if you're not used to doing this) - but its the lazy fix to shoot under any light.
The only problem with using different sorts of lights for studio-esque shots is when each light is a different temperature, and then... its annoying to fix the colour temperature for each and every different light.
Very true but this blog was just to show that you don't always NEED expensive studio equipment and that you still can shoot 'studio portraits'. I always shoot RAW, but I like to adjust the white balance before because after shooting it takes more time, unless you do a batch edit.
All you need is light :) Just anything that generates it and absorbs it or reflects it. I'd rather spend $2k on lights than $2k on cameras or lenses at this point!
(They don't even have to be photographic lights!) - Just... lights! :D
Right ... without light, no photo. As simple as that.