2000SF say? That's huge! Have you purchased the lot already?
You gotta do your homework down to the last detail. Getting permits and materials can be challenging. Rebar in Belize is very expensive, if you can get your hands on it. (You may have to get it shipped from the States).
I've heard Mayan Concrete is the best builder quality. Mahogany in Belize is locally produced and I think it's absolutely beautiful, for exterior or interior. If you buy these materials you'll be helping to support local economy.
You also have to get building permits from the CC Town Board, but you may have to do some permit filing in Belize City. You have to have permits from the ground up; laying the foundation to installing utility and gas lines. (WASA, BTL, etc).
The gas thing is a tricky business. Most folks and some businesses buy a butane tank and run a line through the wall to the gas appliance.
You have to purchase refills from a gas truck on rounds or a gas "farm" in lots. I would reccommend installing a main gas line if it's permitted on Caulker.
You also have to lay the foundation - concrete slab? Sand fill? Drainage system is crucial, especially for the rainy season.
Cisterns are commonly used for roof runoff and can undercut your water bill. RotoAqua (sic) is a popular brand of cistern. Hurricane resistant shudders and sashes and good weather proofing also a good idea.
Your project would bring much needed work to the Caulker community! Most righteous thing!
I highly reccommend you're there on-site for every phase of the build, unless you have a foreman or project manager or both whom you trust.
Depending on how much of the work you're willing to do yourself (labor, leg work, and paper work) for a house this size it could cost about $150,000.00US (or double that in Belize). I don't know if this is high or low-balling, but new taxes are going into effect as of March, with increased prices for materials and real estate fees.
Best of mouth is the word. If you have friends on Caulker, refer to them for resources and contractor referrals.
Here's an article: http://www.belize-real-estate-services.com/building_construction.htm#top
I used to work in property inspection here in Cali and I've spent time in Belize observing and talking to people. Sadly a lot of homes I've seen were half done or poorly contstructed because the money ran out, the workers bailed, or the material couldn't be acquired.
It's your baby, so raise it right.