Depending on where you live, the best option is to rehab NOT build new. Having done both, depending on what you do in the rehab, it is cheaper to remodel than build new. There are too many costs new that you have to take care of - school fees, permits, architect, etc that add into the cost. It isn't a good idea to look at the cost per square foot because you will find that remodel is higher but you aren't paying for ground up on a remodel.