Here's an excellent resource for information on the home office expense deduction and requirements for same.
(There's no point in re-inventing the wheel....)
Per the IRS, "If you use part of your home for business, you may be able to deduct expenses for the business use of your home. These expenses may include mortgage interest, insurance, utilities, repairs, and depreciation. The home office deduction is available for homeowners and renters, and applies to all types of homes, from apartments to mobile homes. There are two basic requirements for your home to qualify as a deduction:"
Continued at: http://www.irs.gov/businesses/small/article/0,,id=204169,00.html
As always, please call if you have any questions about this or other matters.
And thanks for stopping by!