Somewhere over the rainbow!
First of all, love the name. It may be difficult to get your builder to pay ALL closing costs and pre-paids as it is hard to calculate these to the penny. Many factors come into play,
The closing date (pre-paid interest will change),
Taxes ( as it is new construction, not sure how the lender will determine future taxes) you hope they calculate the future accessed taxes after the home is finished, but sometimes they don't and your escrow is short, but that is another discussion).
So, the much anticipated answer here is: get the builder to pay a % of the purchase price, then as you negotiate up or down the percentage changes which helps you better cover the closing costs associated with the purchase. With todays low interest rate, there is nothing wrong with putting as little down as possible and financing as many costs as you can. :)
Good luck! Mirna