Get a firm price from a quality builder.
Then pay in in steps after satisfactory completion of each stage.
say a $200,000 house
$40,000 down to start
$40,000 after foundation
$40,000 after Framing and shell is complete
$40,000 after drywall is complete
$40,000 upon recieving your C/O
In most regions, A building inspector has to approve after each one of these steps anyways, so once he has stamped yor permit, I would release the funds