Cement Floor Preparation

[bookman51]

Folks, I am a newbie to the list.

I am having built a 40' x 72' pole building by Wick as a shop and storage shed for my antique tractors. There will be a cement slab (40' by 32') for the shop area. I am just getting the builiding up for now and will worry about electricity, heating, etc. later. However, right now the slab will be 5+" with fiber.

My questions are:
1) what are the merits of putting a vapor barrier under the cement;
2) what are the merits of putting foam (and what type) under the cement; and
3) should I also use rebar in addition to the fiber

All in relation to additional costs!

Also, what do folks recommend as site preparation. I have built up the area probably 12-16" above the surround area; have three or four inches of cement gravel (as it is called here); packed it by driving over it with my tractors; and it has rained on the area three or four times (good 1" rains or more); should I do something more?

Lots of questions for a newby, but I appreciate all the help. Do not plan on building this building more than once. It is housing my retirement projects for me!!!

Thanks in advance

bookman51