What controls are in place to protect the slabs sent to you by sellers while in your possession? I mean, is this being run out of a house or a secure facility? Are there multiple individuals involved, enough that the possibility of a rogue employee taking off with a ton of slabs is an issue, and if so, is everything fully recorded and insured while in your possession? And how do you plan on resolving it when a seller inevitably insists that a book you received damaged was perfectly fine when it left his possession (basically insisting that you must have damaged it). Is there any video recording/documentation taking place, to protect both you and the seller? Is there any different protocol for how you handle/transact a $5000 book, as opposed to a $100 one?
Also, you mentioned that you plan on eventually offering raw books; how will that work? Are you going to go on a "gradeless" system, purely going by seller descriptions and pictures, with you just verifying the correct book/printing (if applicable) was sent? It would seem impossible to "verify" any kind of grading system on raw books as a 3rd party, as there would be so much subjectivity involved it would be a nightmare. You're also - again - going to enter an area where sellers are going to insist that you must have damaged their raw books when handling them.