Depending on the finishes, square footage, whether the home is one or two stories, how many bathrooms, how large the kitchen is, etc a custom builder can start at about $100/sq ft in my area when there is no land cost or real estate fees involved. There would be additional costs to remove the old structure.
I'd go to the Home Builder's Association for your area, look up custom builders/general contractors (as production builders don't do this type of work), and start to get some bids for your area. You may want to have in mind the type of structure you are looking for, ie an "1800 sq ft two story 3 bedroom 2 bath" home, and get some ball park initial estimates using the same basis.
If you're looking for home plans, Frank Betz Associates online is a great resource.