Charlotte's zoning reguations can limit the amount of square footage of an "accessory" structure. The dfferent zoning classifications will also dicate setbacks, placement, etc. Then if yoiu are planning to build, you better have a lot of patience to deal with building standards. Note:Most of the actual building inspectors and some of the "main office" employees are pretty good people and will try to work with you. But many of the "main office" employees will give you wrong or incomplete information and take NO responsibility.
If you're looking at a newly constructed house with that size garage, you better have deep pockets and the time for custom building. Most subdivisions built in the Charlotte area in the past 20 years have mandatory homeowners associations (not to mention the small lots) that will severely limit the possibilities of expanding an existing garage or building a separate deteached garage. Many communities have restrictions and covenants that virtually prohibit anything additional structures.
If you mean a "new to you" home, you best options are either to check out the older neighborhoods or look in the surrounding towns or even counties.
As a long term Charlotte resident and taxpayer, I could turn this into a book. Instead if you want more info you can contact me off forum.
Mark
RLOP Regular lurker-ocassional poster!