To your question, I think it's too early to lock. Your lender choices will be limited and/or you will have to pay much more to lock up a rate. You should, though, investigate float down policies w any lender you're considering.
As for all the other stuff in this thread, I'm not sure I agree with a lot of it. From the consumer perspective, I'm on my 2nd new construction purchase. On my first, I used the builder's lender. I only looked at it from a #s perspective. They were giving $20K in total incentives, so it was a no brainer even if it had a higher than market rate.
On my current build, I've decided to pass on the $3K in incentives and use an outside lender. Usually, a builder's lender will try to match your rate, so that's the best of both worlds -- keep the incentives + get a better rate. In my case, my rate was so low, the preferred lender wasn't able to match, so I will just eat another $3K in costs by going w an outside lender.
They're not a scam. You have to look at the #s. I suggest doing a comparison in excel of your total outlay for 5 yrs, 7 yrs, and 10 yrs. Whichever is the lowest is what you should be going for depending on the time horizon that fits your profile.
