If building, don't go for max sqft/$. You will be pretty frustrated in like 3-4 yrs. Little things matter. Get high insulation value windows and doors. Max out insulation in walls and attic. If you have rooms above a garage, have them insulate the garage ceiling as if it was the attic and make sure they insulate the garage walls. Also, insulated garage doors, not the cheap Masonite ones. After that, upgrade carpet. Builder crap wears down noticeably in less than a yr. Get hard woods if you can swing it.
Buy up on the dishwasher so it don't sound like you left the garbage disposal on.
Get a paint job where they brush/roll back after spraying and do a complete caulk job in prep.
Make sure those fuckers put drip edge and flashing over all windows and doors, as well as at the rake of the roof.
Make sure grade never slopes toward the house and that the yard drainage is graded adequately to move water.
Make sure they don't freeze concrete if pouring in cold.
If you can afford it, tell them you want 9' ceilings I the basement, or at least the walls poured so that the ceilings can be 9' when finished.
Also, watch out for undersized ac units. Lots of starter guys put I small ones that run rough ridin' constantly.
Lots of other stuff too. Things like home building are super easy to cut corners. Your builder isn't your buddy.