Welding rig question

When welding sheet metal you need a backing plate made of copper or aluminum. This will prevent the "blow Thu" holes common when welding thin metals.

As for what brand of welder to get. Buy the brand that has the best support in your area. Welder are expensive, but you get what you pay for. I use ESAB welders, a brand that many people never heard of. Also you can buy a used unit. Just try it out before you load it up.