I would have to agree that Lincoln are one of the best, but they are rather expensive for occasional home use,
I recently bought a CIGWELD Weldskill 170 TIG welder. Forgotten how much, but it wasn't unreasonable.
It's compact and goes as low as 5A, perfect for thin automotive metal.
Tungsten welding rods are not cheap and you will need a few when you start out.
You can also use it to arc weld, just remember to swap the leads over or else when you TIG, you will melt the tungsten rod,
ceramic gas lens, collet and collet body, and generally end up wondering what the hell went wrong.
Not that I'm speaking from experience.
If you can stretch the budget to get an AC/DC model, you can also weld Aluminium.
Hiring gas from BOC is a pain but heaps cheaper than the disposable bottles.
All in all I'd say for auto body work, the low amps and neat welds of a TIG make it the obvious choice.