$100 per square foot will probably get you in the ball park. Now whether or not that's an outfield in Los Angeles or the dugout in Toronto, that's all up in the air until you do a LOT more research. Don't forget to talk to the bank. In the current restrictive lending environment, you may not be able to get a loan for what you are planning. (A half built home isn't much collateral for a bank, and you don't have a track record about getting one complete like a contractor will.) That's not a problem with an all cash build, but if you are planning on any type of financing, you will have to meet the terms and conditions of that financier. There are so many elements that go into "just getting it enclosed" that you may not realize what you don't don't know. There is site engineering and grading. You'll have to meet the new flood setback restrictions. That alone can cost a pretty penny depending on the location and elevation of the lot. There is foundation work, which if you are in a flood zone, can be a huge expense. There is rough plumbing, which will have to more or less be in place before any foundation pour. Basic framing can take a month on a simple house or 3 on a complex one. And then you have windows, doors, and roofing that must occur before a home can be "dried in". Those can also vary widely in price based on location as well as brands and upgrades. All of these items add up. There is no way that a stranger on the net can add them up for you. You need to do more location based research, and talk to banks, building codes officers, contractors, and individual trades. These too will only give you a rough idea of the ultimate costs, but at least they will be more in your ballpark rather than the Red Sox or Twins ballpark.

Thanks for all the messages. When I first got this quote, I hadn't priced furnaces ever. I had told the contractor that I did not need the Rolls Royce of furnaces because we do not expect to live here more than another 5 years, and he came back with this quote. After talking with some other contractors the past couple of days, I am realizing that there are less expensive options than the Infinity model (including the Performance series from Carrier, which can also qualify for the current tax credit). I am now getting bids on similar efficiency models from contractors that use Rheem, Goodman, Carrier/Bryant/Payne, and other models. Thanks for the help on this question. After this weekend, I'll probably have another question asking for help in comparing models and their prices. I have to act quickly on the furnace because ours was diagnosed officially yesterday and the primary heat exchanger is cracked, which didn't surprise me. Have a good weekend everyone.

Thanks so much for the "to do" list. I actually have a friend who is an architect, so that might help us out. It's a rowhouse, so it's not as though we can do any complicated curves or other designs on the structural walls. We want to do as much of the work ourselves as we can, but neither of us is willing to work with electricity. We're OK with plumbing, but given that the house was owner-rehabbed before and not done very well, I'd rather pay a professional to get it straight. We were hoping that we could move the tub into the house before the extension is built because we want a nice clawfoot, which will be impossible to get down the stairs. But all the interior design we can take care of. I'm an artist and have many plans for the interior.

thanks everyone for your input....has given me an idea of what I might expect. Would have done this several years ago, but could not find a contractor in the area who was doing remodeling....the new construction was so much more profitable and probably less problematic. Now that construction has slowed, I'm hoping I'll at least get some callbacks! Ron6519-thanks for straightening me out about how the separate structure doesn't save $ and hendricus..sounds like a great job you did - great to have those skills! Thanks all.