If I buy blank skateboard decks and make my own designs on them, can I legally sell them?

Would I be able to do so without a permit of any kind and would it be like copy write to use blank decks from the local shop?

No problem copyrighting your OWN design, you could be in trouble if you print someone elses design on the board.

One thing you need to consider with such a high risk product is business insurance. Lots of people get hurt on skateboards, and you could be liable if someone gets hurt and wants to sue, even for just putting a design on a board.