I used to own a pretty nice Century welder (300 amp ACDC with infinite controls and 60% duty cycle with it all the way up), but that has been 20 years ago. Towards the end before they went under they were private labeling welders and plasma cutters for Snap-on, Mac, etc., and for the time they weren't too bad.
Plasma cutters have moved on to electronic controls, which make them easier to start the arc and keep it going, cut thicker steel with less input amperage, give you better control, and in general are more reliable than the old technology.
That unit is not worth more than $200 at the most, and even at $150 I would pass. It is the equivalent of the Harbor Freight welders, in that too cheap means that it isn't good enough to not aggravate you a fair amount trying to use it, and it will use up a lot of consumables. Assuming that the torch is original, you would probably have to replace that to get it to work halfway well, and that would be another $150 and some work to attach the new torch to the old cutter.