Brad:
I would recommend the 135 amp or so MIG machines from any of the major manufacturers (Hobart, Lincoln or Miller). You need to purchase a bottle so that you are using Argon/CO2 shielding gas with the machine rather than flux core. They run off of a 110 volt circuit and will easily weld the 22 guage and 18 guage metal that you are working with. One trick on the thin metal is to back up where you are trying to weld with copper. A piece of copper water pipe flattened on one end is the standard made at home tool for doing this. The welder that I have is the predecessor to this machine from Lincoln that I bought from this outfit. It has worked flawlessly:
http://www.welders-direct.com/merch...p;Store_Code=WD&Product_Code=K2688-1

I hope this is helpful.
Regards,
Steve
New Orleans