I think everyone has pretty much given the same answer - hire a buyers agent. And that is good advice - actually its a no-brainer - after all, buyer agents are free.
I will up level that answer - you need to know a lot more about new construction homes than the sold prices - including many things you probably never thought about. Unlike resale homes, posting new home sales data to MLS databases (only agents and brokers can access) can be delayed significantly. There is a way to find these prices faster but that is propriety info. And with all due respect, you need to understand the data and how to apply it, and how to adjust it so you are comparing apples to apples. A DIY negotiation approach against the builders experienced agent doesn't stand much of a chance, and if they do give in on A, they will make it up on X, Y, and Z, and you likely won't even know it happened.
So bottom line, when buying a new construction home (and more so when building a new home) there are way too many ways for things to go wrong - you don't just want to hire a buyers agent, you want to find the best buyers agent you can, and one who is experienced with new home sales and preferably knows new home construction.
I just came back from checking on a home under construction for a young couple who are clients wanting to buy a new construction home in a development near Bridge Mill in Cherokee County. I am about to let them know why they don't want the new home they were considering - it is a combination of poor quality work, a nasty builders contract, a poor lot, and not such great market trends. My clients were not aware of any of this, and at best, an ordinary agent would have only caught the market stats - assuming they hired a reputable and skilled agent who cared more about the clients long term purchase performance than getting to a closing table. The contract clauses I can mitigate, but not the other things.
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