"The best fertilizer for a field is the footsteps of the farmer...."

and

"the devil is in the details..."

If you plan to operate on online or catalog book selling business it is a good idea to keep faith with both these concepts.

Keeping on top of your inventory means more than repricing; you have to maintain the books in the condition described and in a way which allows you to find them easily once they sell. Also plan on some sort of inventory numbering system, even in the out of print and collectible market, you will end up with a surprising number of duplicate copies which will usually not be interchangeable.

It also means tracking your costs, not just inventory cost, but packing material, shipping costs, online fees, ALL expenses....the devil is indeed in these details.

And finally, expect that sometime in your book selling career that there will be an economic downturn, or a system failure or a family emergency or some combination of disaster scenario and keep funds and contingency plans in place for when something does happen.