@FlyingDonutsaid it best, “Talk to your tax guy”.
I am not in the comic business for profit but I am an independent contractor (1099) with an LLC. I deal with payroll, quarterly taxes, yearly estimated tax, expense reports, etc.
#1. If you don’t have an accountant I suggest you get one and consult them. Especially if you plan on selling a significant amount or any high dollar books.
#2. Document everything, I mean EVERYTHING! Bags, boards, grading/pressing, insurance, price paid, shipping, etc. If you haven’t been doing so I suggest you do. It might take you months to catch up but it will be worth it in the end when you decide to liquidate or sell off that big key. When dealing with taxes you need to have your “ducks in a row”. If the IRS comes for you they will attempt to get what they believe is owed to them right, wrong or indifferent.