Bsch4477: What you say makes perfect sense, but I don't think this applies to the home office deduction. These are my notes from IRS Publication 587, Business Use of Your Home:
Part-year use. You cannot deduct expenses for the business use of your home incurred during any part of the year you did not use your home for business purposes. For example, if you begin using part of your home for business on July 1, and you meet all the tests from that date until the end of the year, consider only your expenses for the last half of the year in figuring your allowable deduction.
