The cabin is the shell around all the systems, and it is the part the county cares most about. The choices that matter off-grid are not the finishes; they are the foundation (frost depth, slope, access for a drill rig), the roof (snow load, metal for rain catchment), the insulation and air sealing (which set the heat bill for life), and the entry (a mudroom and airlock are a heating system).
Permits come before lumber. The paperwork post walks the order; the laws pages say what your county requires; the county questions download is the script for the phone call. Build small and tight first, and add later, because the first winter teaches you what the second building should be.