We have a lot of sink holes in Orlando (sandy soil) and that's not something to mess around with!

They also had a soil test done in 1991 and the result came in fine.

With heavy smoke damage, I recommend budgeting to paint the units as well, using a shellac based primer underneath to seal in as much of the smoke as possible. 

“What type of soil is the house sitting on?”

I had new windows installed last summer and when I moved their furniture, I could have easily filled a contractor bag with what lived underneath and behind it.

When the toilets backed up, the pumper only pumped the new tank, not knowing there is an old one buried underneath.  

I don't think the site is generally more costly than the structure build until you start getting into unstable soils, steep hillsides or other things of that nature. 

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Prefer to have no load bearing pillars if we can avoid them without too much more cost.We have soil and elevations from site survey just passed to us by the seller so shouldn't be a problem, but we still have to select our civil (should be by end of the week).As per insulation requirements would we have to ask the county or how would we figure that out?

unless you own the land underneath you will be paying a monthly land lease to the park owner, which at least in my area could be $800 per month alone, closer to the beach it could be $2,000 per month for the land lease.