Vampire's Ghost. Immortal Keeper Vampire Paranormal Romance Series, #1

Drake Vohjol is a centuries-old vampire with a single mission: grow his blood-for-sale business. He's not interested in becoming a patron to a fledgling human woman who needs help developing mysterious skills. Unfortunately for him, he's a vampire of his word, so when he is accidentally assigned to become patron to one of those Chosen humans, he grudgingly does as is required, not expecting Kartina Gomez, a stunning, innocent young woman who, skills or no, he wants in his bed. Except the rules are clear: the relationship between patron and Chosen must remain strictly professional. For this Viking-turned-vampire, raiding and pillaging wasn't half as challenging as keeping his hands-and fangs-away from Kartina.