What are low cost circuit and PCB design software?
Kicad is free and open source, and it is a relatively well-integrated package of schematics and layout editor.

gEDA is free and open source. It is older than Kicad, has more tools which produce nicer output, but is less well integrated.

Since they are open-source packages there are no arbitrary restrictions on the free version (like e.g. board size in Eagle) and no license hassles.