(petitioner, airline pilot with side business as real estate broker, reported large loss from side business on Schedule C; as for trip to Hawaii, petitioner claimed business expense deduction for cost of airline ticket for unidentified third party; alleged purpose of trip was to scout potential properties for unnamed client; claimed expenses to Yosemite National Park also undocumented, along with unsubstantiated expenses for trips to other places; all expenses denied and court upheld denial for lack of substantiation).