Well i decided on my shop finally. its this type of building
www.us-buildings-direct.com/Assembly.aspx

i found a 20x30 for 2600 bucks.

i have a few questions how thick of slab should i pour i was thinking 5 inch with a healthy dose of rebar.
do i need to poor footings?

This will be my woodshop and toy storage (atv's cars trucks)

i also want to put a loft in the back like a Man came thats 10x20  havnt figured out the best way to do this do to the curved sides of the building.

also what are my options for insulation?

As for the Insulation, check out the spray foam type. It should adhear to any surface and makes it pretty tight and even.

What part of Florida do you live in?  You are likely to spend double what you spent for the kit in concrete alone.  A 5" slab is a great start, but the perimeter footings will have to be pretty big to hold everything down.

Let me see what I have.