Here's the problem. If no one on your crew has ever worked concrete, there are 100 different mistakes that will cost you a lot of time (extra $$$) or a poor job (you'll regret it for 20 years +) or cause the whole job to be a failure (cost of the job, removal, and redoing it right = about 3 times letting the pros do it).
With the wood & sheet metal you can spoil a piece, or stop a day or 2 to ask questions or wait for your buddies to follow through on their promises - you mentioned before that some didn't make it to help with the roof like they promised. These little setbacks only cost you time and a dollar or 2, no big deal.
With concrete, you have that day, a few hours, to get it done right or it is a total failure. Think very long & hard on this. Rethink it again. Any problems or questions come up, & you are out the cost of the concrete & probably have the problem of dealing with a botched pile of 'crete. Jumping into this with zero experience can be _very_ costly.
What I would do is spend my money on putting a couple epoxied bars into that bedrock like has been discussed several times, bolt those couple posts to the rock so it is solid, and concentrate on the roof & walls. You can always lay concrete in a year or two. Dirt floors are fine. I think this would be a good use of your time & labor, as limited is it is. It will give you a good shed as soon and as cheaply as you can, with the least chance for a real foul-up that will cost you very much $$$.
In most cases a slab floor should _not_ be anchored to the poles of a pole building in the first place. That is kind of a real bad idea in _my_ area where we have deep frost. It might not be as bad an idea where you are, but it still is not the proper way to go. The poles are anchored in the ground or bedrock, and the slab free-floats on the ground with spacers between the concrete & poles. They should be able to move independently of each other a little bit. Your plan would be a big mistake here in my cold location.
Fruther, how well are you going to prepare your sub-floor if you are this short of funds? You should not pour concrete on black dirt with organics in it. That is a failure in a few years. You at least need to remove the black dirt & put in 4-6" of good gravel. Then tamp the gravel & use rebar for the concrete. I fear you do not have the funds to make a good concrete floor at this time, and a bad concrete floor is worse than worthless.
The ideas the others have for insulation, waterproofing, anchore spots, drains, etc. will make a world of difference in how well you enjoy your building over the next 20 years. You can build a miserable awkward hole of a building, or something that you enjoy being in - only difference is a couple 100 bucks and a month of planning. Please give the floor some thought & design - these additions will look real cheap to you in 5 years when it is too late to do them.
What to do????
Anchor those posts to the bedrock, it will only cost $10-15 a post and be far less work that the floor, get your roof & walls done and have a fine shed.
Deal with the floor in a year when you have the funds to do it right.
My opinion. /forums/images/graemlins/smile.gif I enjoy watching the progress of your work, thank you for sharing this project with us. /forums/images/graemlins/smile.gif
--->Paul