How do you handle your TAXES - Schedule C?

Obviously, whoever buys and sells storage lockers for a living, is operating a retail business (Selling and buying merchandise)

The part I'm having trouble with is this..

Say I buy a storage unit for $1000

So my Beginning Inventory is $1000

I sell say $1500 dollars worth of that inventory (in which it might be say 75% of the locker) but that in no way means my ending inventory is $250.. as the remaining 25% might be either all the pristine items that I haven't found a value for yet, or perhaps all the garage sale stuff that might add up to $50 bucks.

How do you determine what your ending inventory is for that year, or do you just estimate that it's $250 remaining..  It's hard because, you're not buying specific items with a specific cost and estimate the cost of good sold to be $750.

If you get an audit, what will the IRS say. This is the only part that's guesswork, because the value is subjective.

As far as I'm concerned there is no left over inventory, it was all sold. Anything that might be left and then sells goes on next year's taxes as a sale.