Those $109 units aren't mig, they're wirefeed, and they suck. Mig stands for metal inert gas, so you need argon/co2 to shield the weld, which flows from a bottle up through the gun. You use solid wire, and the gas is the flux. It keeps the spatter way down and makes a nice clean weld on thin metal. I have a Lincoln Migpack 135 (135 amp 120 volt) that works great, it comes with everything but the bottle and gas. You need to spend at least $350 to get a usable setup.
