Have actually known one or two near where I live as well. People who got into the wrong things, met the wrong people and asked too many questions. They buy fresh animal blood at the supermarket to live off----very cheap but not by any means tasty stuff. I've heard its a bloodborne disease. Meaning, you get it by opening your veins to contaminated "vampire" blood. But who knows.
To be clear, the two I met didn't enjoy hurting people and felt bad asking for blood. They would only "turn" people they had known for a very, very long time. I didn't stick around long enough to find our how long.