flooring, granite are expensive, but the structure is even more expensive.
If the design is done by a local firm, ask the designer who is a good builder.
There is something called cost plus, meaning the builder will charge a percentage fee (15-25%) over their "cost".
Now that opens a lot of loopholes for them to make even more money, you are dealing with a totally different animal.
That is why I said, buying a built home, or a stock home would be a lot easier.
Being your own general contractor needs a lot of knowledge from you. The key is to find a good subcontractor, to manage them and make sure they do a good job. It is definitely doable, it just takes a lot oof time and energy. I was told 1000 hour of preparation, maybe 2000. You can save money and get the feature you want, but it is just a pain on the butt to do it.
Either way you choose, please keep us posted.