One good thing that's on your side - many homes in South Florida qualify as "green" but are not being properly marketed as such. I can help you identify those homes, just give me a call or email.
I have a lot more information about green and eco-friendly home buying and selling - visit my website at http://www.devensellsflorida.com/go-green/.
In brief there are no free lunches in this industry, as better construction methods keep being developed and building codes amended, mass production of new systems will with time lower their price and make them more affordable. Meanwhile there are a significant number of small project one could do to an existing structure to make it more efficient in energy conservation and hence more green.
For examplle :-A tight building envelope and good insulation might cost a little more but when then the HVAC system that is required will be much smaller thus saving you money, one cost cancels out the other.
Here is an article on a Net Zero Home that cost about 3 to 6% more.
And here is a home that cost $122 per sq ft to build, avg cost in Ct is closer to $200 sq ft.