Just my opinion, with no special expertise:
You didn't take out a loan, and you are not paying any interest, so you have no deduction for interest. The change order just increases the total price that you pay for the home. The additional amount is included in your cost basis. The fact that the builder intends it to cover his financing cost is irrelevant.
The builder cannot give you a 1098 because he did not make a loan to you and you are not paying interest to him.
There is nothing for you to report on your tax return for the year that you purchase the home.
Other people may have different opinions.
