It sounds like you are tighed up in knots:
First of all, please don't lose this dream home for a few thou; you are talking $10-$20 per month.
You are buying a HOME first, and an investment second: In a few years, you won't care what you paid.
If you are not in a multiple-offer situation, you may get it for $105 and you shouldn't have to worry about the Appraisal. If you offer more than that, you would have to pay the difference, and if you offer less, you may not get it.
Don't worry about New Const vs Old Const; the Appraiser allowed for this in the appraisal: He worked with what he had. Comps are Comps.
Good luck and may God bless
From my understanding, the contracted stated that if property appraised lower then sale price, then I have an option to forfeit or renegotiate the offer. I also did a Ernest escrow deposit of $ 10,000 towards sale price at end of closing. Hopefully I would get that back if I decide to withdraw from this contract. The seller did mention it will be refunded, when we where executing the contract, but who knows, I could have got played!
Something is only worth what someone is willing to pay for it. I would focus on the recent sales in the building and compare apples to apples - look at what other people have paid for the units in the building and that will give you the best indication of value. Try to stay within the last 6 months of recent sale.
Builder models tend to sell for a premium because of all the upgrades and decorating they put into them so consider that as well. There is value in that which may not really be accounted for in the appraisal.
Appraisers are also always behind the market. They are looking at the last six months of sales, not what current buyers are doing. This has caused some issues in markets that have turned up rapidly. I experienced it in my own market.
VA appraisals are notorious for coming in low - so much so that there is something called the Tidewater Act that allows a buyer to contest a VA appraisal by providing a justification for the sales contract price. The reason homeowners were refusing to accept offers from veterans using VA loans - which killed the whole intent of the program - so they passed the Tidewater Act. I've actually had to do entire appraisals on VA loans because the appraisal was so off. Just another story to help you digest the differences in appraisals.
Bottom line is its worth what its worth to you and what you are willing to pay for it. If you haven't made an offer yet, use the $105k appraisal to try to get the best deal you can. Use an agent if you aren't already. Buying from builders is a lot like buying a FSBO.
I would do two things, first I would be very aware of the appraised value. Appraisers compare the home to homes that have sold recently in the neighborhood and that have similar square footage and features as the home they are appraising. If they can't find a home that is directly comparable, they will find homes that are as close as possible and then adjust their opinion up or down accordingly. Therefore, more than likely your appraiser took into consideration the new vs. lived in value of the home when making his conclusion as to value. Second, if you are using a realtor (and you should be! Typically the seller pays the realtors' fee so the service is free to you as a buyer and that's a deal you should not be passing up!) talk to them to get a second opinion as to current market value. Then make a reasonable offer and let the builder either accept it or make a counter offer.
I doubt the price is going to drop $20,000 just because the home is no longer 'new construction' but even if it did, you are BUYING new construction and not resale, so... Best advice is to make a reasonable offer and see what happens. If you don't like the response, you can always buy a different home, perhaps a resale home, and see if you can't get a better price.