It's not terrible advice tbh, even just hand sketches are solid for getting ideas down, makes it easy to translate to cad. It at least helps me think things through and the like.
Get a few pencils with different leads (some harder stuff like 2-4H and an HB) and some nice paper and you're good, but really anything works, totally have a mockup of my garage on a whiteboard planning where I want to put stuff.
As for cad packages, freecad, as far as I'm aware there are some architecture workbench plugins, and there's a tech drawing workbench. Coming back to cad after a while I found it super easy to pick back up (coming from solidworks at least)