Well, there are certainly a couple examples of such in the books. Werewolves and vampires are the simplest and most obvious examples. You could also easily play someone who was completely ordinary until some sort of artifact (e.g. Denarius, or even a creature like Mouse) "chose" them. Wizards are probably not a real option, as it takes a lot of training to develop the power, so there wouldn't be the sharp demarcation of "normal life" vs. "abnormal life."
I disagree with your assessment of the wizard as a viable character for my specifications. Though an individual's power may, initially, be far from what it will eventually grow to be, the realization that such power is within one's grasp may bring about the sort of psychological alteration that I seek in a character. The differential between the normal, mundane life and the supernaturally inclined life would be more than substantial by that actualization alone. You have my gratitude for your reply, nonetheless.
Will it be possible to be a character that is an average, mortal human being and have him progress to Wizard status, for example?
Yep.
What if my character has no magical skill? Are there methods available to somehow increase his skill and give him the same heavy-hitting properties as Dresden's potential?
Yep.
Also, are there other magical beings available to play such as a Knight of the Cross?
Yep.
I basically want a powerless character that comes into power to explore the psychology of such a transition, and I am curious as to what extent the RPG will allow me to create that experience.
Baked right in.
Thank you for your input.
Fred, you are funderful.
Are you insulting me by complimenting iago and, by extension, his terse responses to my questions incased in a comparatively long-winded post which, by implication, means that you find mockery in my writing style?
I think that was a viable joke, but a lack of a sense of humor makes me doubtful.