I see you are in the Maricopa market area, as am I. Being familar with the market area, I would hope the comps you are referring to are also manufactured (similar in age and built after 1976) and on similar size acerage. As for "permanent foundation", are you referring to a foundation slab, runners, or footings, with support stands? also with approved tie-downs?
If you plan of getting financed, there are other requirements of the property. Such as the HUD seal labels must be attached and visable on the exterior, and builders certification label. Along with meeting the requirements for water and sewer systems and location of them. And you will need a copy of the affidavit of permanent affixture.
As Carlos stated, have you asked why or determined why the one is listed at 33% below comps? Perhaps the structure itself does not provide significant value to the overall property, whereas the value (sale price) is only in the land. Consulting with a buyers agent and/or appraiser before hand may be very beneficial, especially when considering a bank owned (reo).