Sweet potatoes, taro and bananas all grow really well in that area.
There was a fellow there who was trying to set up a food forest and be sustainable and all, although he's now moved off island and gotten married and seems to have moved to Canada. But you may be able to find lots of information in the older posts on the websites he had while he was working on his Fern Forest project.
http://sensiblesimplicity.lefora.com/
and
http://sanityandsimplicity.blogspot.com/
For building, as Owner/Builder, you can hire carpenters instead of contractors and save some money. You still get other folks to do the building for you, it's just not as expensive of other folks. Building houses in Hawaii is much easier than on the mainland since you don't have to do all the heating and air conditioning stuff.
Ortho Books wrote a book called "Basic Home Building" which will be really helpful for building a house. It's not very expensive and has loads of diagrams and goes through how to build a house step by step.