floor pans
Yeah I wouldn't buy one of those cheapy HF welders...especially if you are just learning. I'm sure a seasoned pro could get them to work decently but you are going to be struggling with just learning how to weld on your own and you don't need crappy equipment throwing another wrench into it. I'd go with Hobart or Lincoln for a cheaper but still decent quality mig welder. Get one that can be hooked up to gas. It's not totally necessary for floor pans but you don't want to end up having to buy another welder in the future if you're going to be doing welding on the body.
Just remember to get things clean clean clean. My first welding project was doing two front floor pans. The problem was the transmission hump was pretty rusty but not rusted all the way through. I got it as clean as possible but it just didn't weld very nicely along there. Both pans looked real ugly when I got done with them but oh well it was my first time trying and at least they're hidden under carpet lol.