As most folks on here have already said, you'll need a 220 if you want to weld a lot of thicker metal (framework), otherwise a 110 should be fine. I got a Hobart 140 (110v)with gas regulator brand new in the box off craigslist for 250 bucks, and it has served me well, though I mostly do sheet metal work with it. I have done some welding on 1/8th inch plate, but only on small brackets and such. It worked fine for that, but you would probably want something with a longer duty cycle if you wanted to weld a large amount of heavy gauge metal.
Also I would suggest taking a mig welding course at your local community college if one is offered. I took a 10 day course for a hundred bucks, and it was well worth it. All the free wire, gas, and scrap metal I could want to practice on. Plus tips about puddle control, tip angle and other general welding techniques, from an experienced welder. Mig is easy to learn, but it's still nice to have somebody give you pointers.
