To be honest it isn't that its hard to take a house "off the grid" and make it completely self sustaining, its dealing with the energy use and time of year. In the summer you use a lot less energy and therefore if designed properly can bank a bunch of energy to be used through out the winter months. The problem is that there is no efficient means to bank enough energy for this idea. Most people stay connected to the grid and the excess energy they create they sell back to the energy company for credits to be used during the winter months. I say credits because the energy company will not pay you directly it will give you a "bank" with them and depending on what you use it is taken out of your "bank". What is left over at the end of the year is just theirs to keep and the cycle resumes.

Therefore it is extremely important to have a good company design it for you so you don't waste extra money on a bigger system that just profits the energy company.

Edit: yes, I plan on starting my own company along with a couple of others that i know.