If you have a house built from scratch (I am assuming you mean the same builder and same town house community) how much more or less will this cost than if you just buy this spec house and you have the builder finish the room? Is it a wash? Or will the spec home cost more than building from scratch? That's what I think is the most important consideration here.
To be honest, if it's a wash to have it finished, what's the problem? I'd just take the spec house and have them finish the room and be done with it, if it costs the same as starting from scratch. It will be heck of a lot less headache and wait time for sure.
I however, can undertand the hesitation if you are telling us you would be spending same amount of money on this incomplete house as you would just starting from scratch for the same style house but with the finished planning room.
That would mean the builder is overcharging you for what amounts to a home with less living space, and that would be very unfair! And if that is the case, I'd point that out to the builder and insist he remedy this by renegotiating with you a lower price on the spec home since you'd be getting less finished space square footage-wise than what is typically offered for this particular model.
Or demand they finish it at no extra cost since it is afterall the spec home. It probably has wear and tear from people walking through, and so on. Maybe a tougher argument to justify, but it can't hurt to try.
Bottom line, I wouldn't pay anything extra for the spec home if it was a model that was supposed to have more features but didn't. Not because it wasn't what I wanted, or that this was an opportunity to "get what I wanted" but because the builder is cheating you and needs to be called on the carpet! Demand he lower the cost or finish the room to your liking and only then, will you pay what the house with a finished room should cost anyway. If that makes sense. :P
By the way, how much would it cost you to finish the room yourself? Have you gone to a Home Depot or Lowes to find out? I would! How much needs to be done to make it a room versus storage? If it's matter of pulling out shelves and painting the walls, I'd take the spec house as-is if you're getting a significant price cut from the price of a house with a finished planning room.
I can assure you, the cost of making the room livable would be minimal if the change is strictly cosmetic. Even if the room is merely framed up (like an attic with wood beams and exposed insulation) and all you need to do is add sheet rock and carpeting, it still might be cheaper to take a price cut and do it yourself, then to build from scratch and wait who knows how long before you can move in, or have the builder finish the room. They can pad/hide alot of expense in the estimate and labor time if you let them call the shots. The only thing you save by having them finish the room is time and energy. But sometimes putting in the sweat equity yourself is well worth it and better for the pocket book.
If you have the time, do some homework and see what finishing it off yourself would cost. The builder might be over inflating the cost to finish this room in hopes of making a profit at your expense. Just sounds like he's trying to do alot of stuff here. I'm still hung up on the fact you have to pay extra to finish the room. You should be paying what it costs to build a new home from scratch with a planning room or less (even with finishing the room) because it IS the spec home. Hmmm. He sounds like a slick one for sure. Stick to your guns. Do your homework.