If you really want to do this, the value for depreciation is whichever is lower: the purchase price OR the fair market value as of the date when you put it in service for business use. The fair market value is what a willing buyer would pay a willing seller for the similar item in similar (used) condition.
Let's assume the value of a two-year-old printer that originally cost $139 is about $60. Since your business use is 10%, you would depreciate 10% of the value over the class life, which is five years. So you can depreciate $1.25 per year over five years.
You do not qualify for section 179 accelerated depreciation because the item is not use more than 50% for business.
You may qualify for the de minimis safe harbor, which allows you to expense certain items that would normally be depreciated, as long as the value of the expense is less than $2500 and as long as you meet certain other conditions.
In TurboTax, you would enter that you have a business asset that is placed in service at $60 with a 10% business percentage use. TurboTax should tell you whether you qualify for the de minimis allowance or not, but that won't come up in the program until after all of your expenses and depreciable assets are entered.
