There are no Federal storage regulations, but there may be State or Local ones.
You can sell C&R guns while you have your License but you need to be careful. It is NOT a license to engage in business.
For example, if you mail order 2 K31s, pick out the best one to keep and sell the other, then you are OK. Buying multiples with the INTENT to sell extras at a profit is not kosher.
Do I send notice to the county PD or to the local municipality where I live?
I would say local, but that's a guess.