The term pre-fab is loosely used. There are several versions of pre-built structures, from pre-framed wall sections, to modular building block sections, all the way to completely built (interior & exterior) modular homes delivered on site in two or more sections. most manufactures of modular homes offer a wide variety of styles and floor plans. I would suggest finding a manufacturer within a couple hundred miles of your site, to limit transportation costs. If you google "manufactured housing" it should bring you to many sources. A typical modular home is sound, well built and can be ready to move in, in a week or less. If your prep is ready and you have your plumber, electrician and finish carpenter all lined up, the process is fairly easy. Good luck.