In the Western Ky area, New York may be higher depending on your exact area, the range for DIY remedeling is $40-$80sqft. It really depends on how much you do yourself. If you are planning to do all of the work, you may be able to lower that cost. $80.00sqft. will pay for a good high-end remodel, mostly by pros (brick, wood trim, hardwood floors, HVAC mods, plumbing, custom lighting, etc.) New home construction is kind of predictable, but remodeling is more variable. Expect to see a wide range in pricing for the professional modifications to your home. A garage would cost considerably less, but when you consider that you need the foundation and the roof to be done by a pro, there's not much left in between but it could still cost as much as the other work on the house. Check your local neighborhood regulations and make sure that the modifications can be done legally. You can't build all of the way to a property line in most areas. Some areas have restrictions on garages and storage buildings. Check it out thouroghly before you buy.
Tom in KY, Frustration factors pile up high when you can't do what you want with your own property.