Developing a 142 SFR subdivision outside Atlanta, how to structure builder takedown?

I just rezoned 142 SFR 45 minutes outside of Atlanta and I am trying to understand how to sell to builders. I am willing to wait through LDP and most builders will want a tranched takedown.

What is the normal percentage of hard money down for a phased takedown? 

It sounds like I will need some site work for the whole site at the beginning so that the site is not impaired if they walk at some point in the project. 

I am guessing the whole site will need to be cut/fill balanced, sewer and water mains run, all the streets rough graded, erosion control, stormwater management all in the first phase?

What else am I missing or should be asking for from the builders if they want the land in phases? 

How do I make sure I am not at risk if they mess up stormwater management etc on the first phase when I still own the other 2 phases where there is an erosion or stormwater problem?

Thanks!