William, does it have to be an electric welder? Because the cheapest, most dependable used sets are oxyacetylene. You can find these for less than half your budget and they do an outstanding job on light-to-medium thickness steel (up to 1") with little clean-up.
MIG spatters a LOT so if you go this way, figure on using Spatter-Guard sprays and chipping hammers or Sidewinder grinders.
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