How Does Bob the Farmer Become Bob The Magic-User?

I'm totally fascinated by zero level game play!

To be quite frank, I like it because I think it embodies the mayhem, chaos, grittiness, and nihilism of early edition  Dungeons & Dragons. But, I think that others more concerned with story ( the S word!) may find that zero level game play completes a character's story arc for those who wish to play a character from humble beginnings to the zenith of power; from peasant to hero to lord to immortal.

Zero level gameplay makes all the sense in the world when the n00bs transition to Fighting-Men or Thieves. The concept starts to become a bit more trouble than it's worth if player wants to level up his character as a Magic-User or a Cleric. The whole thing becomes a pain in the ass if you add demi-humans and any of the non-fighter sub-classes to the mix. 

A comprehensive zero level mini game that transitions both human and non-human noobs to 1st level character classes would be the way to go, but I'm afraid I lack the resources to make one* at this very moment. In the mean time I'll provide some notes to smooth out that transition from lackey to non-fighting class hero:

Note: I'm only taking into account the three classes from the White Box

• Clerics: I've always assumed that a Cleric's capacity to enact their God's rituals are due to a life time of prayer and devotion. In a harsh fantasy world, were most of the population is composed of serfs and peasants, I always assumed that this type of commitment could only be afforded by cloistered monks and/or crusaders. I think one of the best ways to smooth out the transition from 0 Level Character to 1st Level Cleric is to get a bit creative with our definition of a Cleric. The archetype of a cleric can be expanded to include a lay person displaying stigmata, or a devout person who is possessed by good or bad spirits. Another good example might be that of a flagrant whose scarring of his or her body pleases a God enough to make the human a vessel of it's power. In other words, lets separate the cleric from the monastery. Tim the butcher would become a "Cleric" after he realized that his God's grace possesses his body every morning after he lashes his back until it bleeds. 
• Magic-User: It makes very little sense for any one who hasn't been obsessively studying the ways of magic all of their lives to become a Magic-User. I would assume that it would take someone decades to master the wild and chaotic art of magic before they'd be able to enact a cantrip. Every sorcerer or magician I can think of follows that same pattern. This being a fantasy game and all, perhaps we can overlook that, and we can instead look at spellcasting in a somewhat similar way to the Call of Cthulhu Role Playing Game. Maybe all it takes for a someone to be able to cast spells is to study some sort of sanity draining grimoire. In that case, a Magic-User would be just someone with a strong enough psyche to withstand studying a insanity inducing books of arcane lore and the with enough intelligence to be able to alter reality with the weird mathematics of magic. Then, Eddie the disgraced  Noble, who took up occultism as a hobby growing up, could go on to become Eddie the Magic-User. A Magic-User's spell casting abilities could also be awarded by demons or similar types of alien entities. That would surely cut down on the number of years it takes to master magic.And thus it would be easier to explain away why the zero level character with no apparent interest in the occult or magick went on to become a 1st level magic-user.

As you, dear reader, have probably noticed, I've the zero level characters in my examples careers or professions. Perhaps another method could be to forgo the idea of professions altogether. One could use "Normal Man" instead. (A term used by Dr. Holmes in his Basic Set.) Instead of having a character with an implied story, just play the character using the generic "Normal Man" moniker, and then after the character reaches the first level of his choosen class, a story can be retrofitted. While Bob the Normal Man lacks the charm of Bob the farmer; it is definately easier to see him turn into a magic-user. 

Ofcourse, you can also ignore everything I've written and just level up your zero level characters without any sort of justification. 

 * Perhaps I'd write one if I could manage to get some startup money, start my own vanity press and comission artists to illustrate my 500 page magnus opus that wouldn't only include rules for zero level game play, but also my crackpot interpretations of various philosophies of a pessimistic bent and weird pseudoscientific essays on medieval life.