Jana,
Everyone is right about the 1004- that is why there is a box for you to check that says, "subject to completion per plans and specs".
Do not forget to invoke a hypothetical condition. If the home is proposed it does not yet exist; therefore, valuing it places you in a position where you KNOW it does not yet exist, but valuing it as if it DID exist is contrary to fact. So the hypothetical is a must.
As an additional option, I also use an extraordinary assumption that the completed home will actually be what has been proposed. Anyone who does these know that the end product is usually something at least a bit different from what had been proposed- sometimes, just interior features (like granite counters instead of formica) and sometimes it ends up vastly different- larger/samller, more/less bedrooms, etc.
Good luck.
Brad Ellis, IFA, RAA