I've had a little AC welder for years and a couple of years ago bought an inverter welder - 180A 100% duty cycle for just over $200.
Seriously look at an inverter DC welder rather than AC. You get a bit more flexibility (+ve/-ve polarity) and its easier to use.
One of the contractors at work was telling me he bought a little gasless MIG for just over $300... I was kicking myself for not getting one of these till he mentioned that they are fine while your are using them all the time, but as soon as the nozzle oxidizes, the wire feed is very troublesome. So it looks like its better for the constant use a contractor may have than the hobbyist.
For those who have gas MIG/TIG setups, there is now an alternative to bottle hire. I'm told there is a supplier in Katoomba, I think, who you can buy bottles of inert gases from (i.e. you can't buy oxy or acetylene, but you can buy argon and nitrogen, etc). There may be others in your local area
. For me the cost of bottle rental has kept me away from MIG, TIG and oxy... I just don't do enough of it to warrant the cost, but buying a bottle at least you know what your costs are up front. I don't know any more about it, but if its like an LPG bottle exchange, then I think it would have to be a winner.
Al.