lots of free cad packages around (rhino is super expensive)
I use openscad: http://www.openscad.org/

Freecad seems quite popular. https://www.freecadweb.org/

here's a few more: https://www.thoughtco.com/top-free-cad-packages-485330

used to be a whole bunch of autodesk free software but that just points to tinkercad now - also free: https://www.tinkercad.com/

A lot of it depends on how your brain works. If you are a person who sketches designs before making and can draw stuff in 2d - then all of the above should suit you.
On the other hand if you're like me, and your brain ONLY works in 3d and you can't draw stuff on a flat piece of 2d paper to save your life - then openscad was made for you :-)
No drawing involved. You just tell it what you want and it does all the drawing for you. And only in solid models that can be exported and printe without any hassle.