The product you are buying for $100 per month I assume is available for resale to customers.
It would be entered in the inventory section under Purchases.
I put an example below, you would enter your actual inventory on your return.
This is how it works
Beginning Inventory $0 Jan 1, 2016
Purchases $1,200
Ending Inventory $400 (for example let's say you sold $800 worth of the purchases)
Cost of Goods Sold $800 This is deduction on your taxes.
TurboTax does this computation when you enter the Beginning Inventory, Purchases and Ending Inventory.
