As the buyer, you should not have to pay anything to use a real estate agent, including for a new build. In a real estate transaction, the seller is responsible for paying the agent's commission, which usually amounts to 6% of the purchase price. With new constructions, the builder is the one who will foot the bill and pay the real estate fees. Most builders view paying a buyer's agent fee as a cost of doing business.

This is important to keep in mind: The builder, in nearly all cases, will not give you a discount for buying a home without an agent. That’s because the fee to an agent comes from a marketing budget, rather than the construction budget, to prevent the commission from impacting their gross margin for home production.

With that in mind, there’s no reason not to use a real estate agent. From your perspective, it won't be any cheaper if you forgo one, which makes choosing someone who can advocate for you a no-brainer.