It has been covered a few times. Here are my quick hints of what to look for, and search for
MillerMatic 175 is a MIG that uses 220 volt, along with gas. It will weld about anything you will ever want on a vehicle from sheet metal to control arms, to frames. I doubt you would ever outgrow that welder.
Shawns MillerMatic 210 is the big brother to that, costs more money (almost double), but is better. The only way you will outgrow that is if you start welding battle ships.
Lincoln makes comparable welders. But my experience is that the Miller customer service is worth paying for, where Lincoln is average. By the way the welders are about the same price
Don't let anyone sell you a 110v MIG. If you do heavy welding you will be upgrading too soon. They work great on sheetmetal, but are not enough for heavy auto welding unless you work real slow.
Don't be shy of an AC/DC stick welder. Not good for the light stuff, but works great on the bumpers, frames, and things of that like. Take a little more practice, but with a few nights of messing around you will get the hang of it.
And last hint is talk to TJJUNKIE (Jake who works for AirGas) before you spend a penny. His price quote was very competitive. Plus the service I have seen at airgas was good.