@TerraDea31 said "My reading is that in order to deduct expenses for storing and selling items we must declare a value for our “inventory”. "
That's not true. Inventory is just one way of determining the "cost of goods sold" (COGS), for a business.
Even though you "are in the business of selling the inherited goods", the items inherited from your relative are personal items, and not business inventory. You cannot deduct any expenses, including storage costs, for the sale of those items. Since the cost basis, in those personal items is, almost certainly, the same as the amount you sell them for, you do not need to report the sales on your income tax.
If you are going to have to report the sales, because you are going to get a form 1099-k, then you simply report the same amount as your COGS.
