To be deductible the item needs to be used as part of a business - and - the deduction is, as others mentioned - a business expense that reduces your taxable business income
. If you don't have any profits the deduction is not worth much. The IRS has qualifications as to whether a "business" is legitimate or "hobby." There are also limits on the number of times (years) you can run "losses" from the business.
Be very careful when taking advantage of "deductions" from a home based business. There are tax implications that will affect what will happen tax-wise when you sell your house. Likewise, declaring your boat a business when it really isn't has been in the IRS's gun sights for a number of years.
From personal experience over the years I have found it less complicated to just keep homes and stuff separated from your "business." It makes things a lot easier later when it comes time to sell the house, boat, whatever.