Quickest way would be to hire a GC that can complete it quickly. Recognize that you're going to sacrifice some quality for speed. If you're transforming a structure into a house, assuming that it's already dried in, find a good finish out contractor in your area.
If you're not worried about having a set of plans, you can go directly with your GC who can perform a design build on it, usually a lot quicker than an architectural firm.