The Hobart Handler 125(can be upgraded to gas) is a pretty good welder, and it runs off of 110. It has no problem welding 1/8 diamond plate and will do 1/4" steel when you grind an edge for welding. New it wont be found for $300, though you might be able to get one used for that amount.

Another option to buying new is to buy a used/reconditioned welder from a welding shop.

You should also check out craigslist for your area.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed