It's gotta be free. It's hobby, after all, not a business!. Creating for-profit software isn't an issue, but anything that requires a hardware mod is out.
No, all of the major consoles, except for the Xbox 360, do not have open development environments. There are various homebrew kits you can get, but these aren't sanctioned by the console makers (Nintendo, Sony, and Microsoft), so at best, you'll only be able to give away ROMs of what you make for free. If you try to sell anything, you'll get sued into the ground.