Think of it this way… you walk into a new build sales centre and you meet a friendly sales staff who is happy to answer your questions and sell you one of their properties. Now ask yourself, who pays this person? Or who’s best interest is this person looking out for first and foremost? Ultimately the sales staff are employees of the builder and inherently working in the builder’s best interest.
That being known, it makes sense to have a Realtor, working in your best interest. A Realtor can help ask the right questions, aid with lot & model selection, review the sales paperwork, and negotiate or advise on upgrades.