Vainqueur the Dragon4 books in series
Vainqueur the Dragon Publisher's Summary
Vainqueur Knightsbane is your average dragon: A giant, fire-breathing lizard who loves to take naps on his golden hoard, kidnap princesses for fun, and make the life of adventurers miserable. Vainqueur's only pleasure in life is to watch his treasure get bigger, one coin at a time.
So when a would-be thief turned unwilling minion tells him about "classes", "levels", and "quests", Vainqueur wonders if maybe, just maybe, he should consider a career change.
After all, why bother hunting monsters for free when you can get paid for it?