The cost per sf varies a great deal whether you build in the states or Belize. Are you buying your wood in SP or do you drive up to Spanish Lookout or Orange Walk and get the wood milled for you and then shipped down to SP. Then you have to decide what wood are you going to build with Cabbage Bark or Santa Maria just to name 2. They cost different. Most houses in SP and CC are built with 2x4's rather than 2x6's. As PedroI said you have to micro manage the project and constantly check what your doing. If you know little my guess is you will get very frustrated and that's if you get a good builder. A bad builder will get you poor. Best bet is to spend at least a month or so in SP talking with builders and with people who've had houses built for themselves.