Someone mentioned getting older - When I designed our house, I made sure all doors and walkways would be 3' or wider in case we ever need wheelchair access. Ramp in from garage instead of step. All on one floor with basement easily accessed from outside. Think about things that might give you trouble as you age.
Having it built will give you more input as someone else also said. If there is chance of high wind in your area, insist on construction designed to take the wind. :thumbsup: