It isn't about the professional shops trying to keep hobby guys from welding, and it isn't about the welding machines, it's more about the POWER SUPPLY. Yes, 120v welders are handy because you can (theoretically) unplug Helen's washer and use that receptacle to build a boat trailer in the garage. HOW-ever, more likely than not, you'll find that the wall plug won't support the welder, at least not for very long. My neighbor has a 120v wire feed welder (Chicago-something brand) that he bought for fifty bucks from a guy who bought it from the guy who bought it at the country fair. NOBODY had ever been able to make it weld. I welded professionally for years, and have a nice stable of machines to use, but needed to tack something in MY KITCHEN (I was building an overhung table for my breakfast booth) so I borrowed the 120v "blaster" from the neighbor. FIRST I had to take it apart and assemble the drive spools correctly, after which I got it to weld for the very first time ever. When I say this machine was "limited" I mean VERY limited. Just about the time you had a decent weld going it would trip internally. I even built a tricky little raised mount for it with vent holes in the bottom to enhance cooling. About all it's good for is tacking something together so you can then weld it with a real welder. Is 240v current so rare that you need to buy something that will gradually burn out every 120volt plug in the place? Just think of an electrician stuffing #12 wires into a plug using those little holes in the back of the plug body, and how little contact that would have. Helen might have a tough time doing the next load of wash. How many times have you ever heard someone say: "Boy, I wish I had bought a smaller welder, with less capability."