If you are looking to save money, the plasma is not the answer.

Junk guys around here use LP gas and medical oxygen on their torches, I would assume it must be cheaper that way.

Plasma makes a nicer cut and takes less skill, hacking up iron for the smelter cleanness of cut isn't too important.

Edit, brand and model-The guy at the welding supply store told me that Thermal Dynamics and Hypertherm were together at the top for quality. I ended up with a TD cutmaster 52, bought from an Ebay seller. Just got it this winter, works great on clean metal.

Use your torch to cut up the scrap, then take the money and buy a plasma.