I would be worried about future liability for cleanup costs if it's determined there is fuel in the soil.

Need at least three acres or more if your soil is rocky.  

You can have two houses that are identical according to the data on paper/ virtually, but millions of dollars apart in value for infinite reasons that you just can't know without being there (level of finishes, condition, smell, same builder or different, how the property will show to potential buyers, micro-location (same sub-division or different one across the street, one has awesome views while the other doesn't, one could be on a lake while the other isn't, one could be next to gas station or on a busy street, near train tracks, a smelly factory, backing to commercial or high density multifamily, one could have settling issues with the foundation because of expansive soils while the other doesn't etc. etc. etc.).

Im from the lafayette area in Louisiana and I have come across a few deals but haven't put any homes underneath a ccontract.

Timber resources, correct soils, agriculture, etc... the real question is 'what are you looking for?'

Find one with an underlayer attached, and if noise is an issue put a sound suppression pad underneath.

Mortar the underneath of the tub ( which is an option in the instuctions).

I guess even if you have the ability to tap into municipal lines, you should checkout the soil conditions to see if conditions are good for a basement or if you have the dreaded shrink/swell soil.  

It was 25 piers that needed to be dug and placed underneath. 

I can tell you all about the engineering properties of soil.