A couple of technical matters.
The floors are made of concrete, not cement. Cement is an additive to concrete.
If its cold on the ground, insulating the slab may be worthwhile.
Do you have far to travel to the site?
I ask, because if so, it may pay to work quickly on roughing things out so its not bad to stay there on the weekends.
If you dug the post holes, set up roof posts in steel and concrete them so they are stable, you can put up the tin roof and wrap something around the poles to break the wind.
Then when you have more cash, concrete the slab etc.
Then you have basic shelter and somewhere to store things like windows, doors sinks bath etc if need be.
Think about having a hot water storage tank of any sort in the roof structure finally.