(petitioner, an attorney, did legal work for brother for which reimbursement was anticipated in current year but didn't occur until several years later; petitioner incurred expenses related to brother's business during tax years 2001-2005 and deducted per diem expenses in 2006-2007 when reimbursements paid; deductions disallowed because petitioner on cash basis and expenses only deductible in year(s) incurred).