Stop by your local welding supply house (you'll be buying gas, wire, and such from them anyhow) and see what they have on the floor in the way of trade-ins or reconditioned (warranty repair) units. Keep in mind that with the lower priced 140 amp models you are usually just getting the transformer and by the time you get a gas regulator you're not too far from the price of a 160 amp which is about all you can typically run 110. The really cheap units don't have an internal gas valve any you're stuck with flux core wire.
FWIW I have a Hobart 187 that I bought from Northern Tool. Got a pretty fair price, but my local shop would have met their price. They still made me a deal on a package of new gloves, wire, gas bottle, spatter gel, a cool auto-dark shield and basic hand tools.
Check you local shop before you pull the trigger online...