My first mig, a Lincoln weldpak 100 was bought to do bodywork. Before that I was brazing sheet metal when needed. It was only flux core so that's what I learned to work with. It was back in the mid 90s so choices were limited. The flux core will work for doing sheet metal work but you will have to clean the flux after welding. But it's a cheap way to weld and no gas bottles to worry about. As far as gas bottles go, call around. Around here each welding supply company is different. I was able to buy a tank (not sure of the size but it's about 3' tall) from one supplier that was twice the size of what every other supplier would sell me. If I know I'm going to be doing a lot of welding I'll rent a full size bottle for a month. Because I own a tank from them they have no problems with month to month leases.