Everything can be negotiated.
Unlike CO as mentioned earlier, the area around Paris, VA is a market where I'd strongly recommend you get a realtor to represent you. Something that has happened before, and looks like we're headed now, is that people are going under contract for new construction at let's say $100,000. When construction is completed and it's time for an appraisal, the values are coming in at $90,000.
You need to include an appraisal contingency in the contract, unless you're prepared to bring that $10,000 to the closing table.
Builder contracts are not the same as the standard regional contracts and the terms can vary widely. The appraisal example is only one element where professional guidance will help you tremendously. There are many other elements that require guidance.
I strongly recommend you find an agent who is very familiar with different types of builder contracts, as well as a great negotiator. You're welcome to contact me at email@example.com and I'd be happy to recommend an agent in your area.