Fred is a professional musician. He performs with his electric guitar at various music halls. He has set up a special room in his house that is soundproof and contains a variety of expensive recording and mixing equipment. He uses the room to practice regularly. He does not use the room for anything else. His business records show he paid utilities and maintenance with respect to the room. He believes he should be entitled to deduct his costs, including an appropriate allowance for the depreciation of the room. What is Fred allowed to deduct, and what limitations conceivably apply?