So I've seen some very good design software, but almost all of it is very expensive. I'm just wondering if there's a good cheap design software out there.
OnShape is free for students and the public and is very similar to Fusion 360. It works online on almost any device and was built by some of the engineers from Solidworks. Free accounts can not have any private documents so anyone can see your design. If you know how to use Solidworks/Inventor you will be able to pickup Fusion 360/OnShape very quickly.
OpenSCAD is also free but works through its own programming language. It requires a strong math background and some understanding of programming to use as it has no GUI tools.