This is definitely an interesting design idea, [MENTION=12460]airwalkrr[/MENTION]. I have a few questions.
1) Are you looking for total simulation in your design? I get that there is no hand-holding and spoon-feeding of PLOT™, but are all of the players essentially being Solo DM'd until if/when they encounter one another in-game?
Excellent question! All characters will begin play in the City of Greyhawk, whether they already live there or traveled there in search of adventure; it is the best place to find adventure in the Flanaess after all! More specifically, it is well-known that the Green Dragon Inn in the River Quarter is a great place to trade in rumors of adventuring locales and hidden treasure. At the beginning of the campaign the starting players will have to make their way to Green Dragon Inn and seek out reputable sorts. Some might be NPCs, but they should all eventually come into contact with each other. It will be up to the players to negotiate the terms of their adventuring company contract (anything from an official document to an unspoken agreement) and then seek out an adventure.
2) If _most_ of the adventuring types are either Fighter or Rogue, what does that mean for the world at large? Are adventuring types common, uncommon, or rare?
Adventurers are an uncommon, but not unheard of sort. It would be rare to encounter a party of adventurers on the road or inside a dungeon. But you might very well come face-to-face with other NPC adventurers (most of whom will be fighters or rogues) in places like the Green Dragon Inn where adventurers, whether retired, active, or would-be, tend to congregate.
Fighters and rogues are common within the profession, making up at least 50% of those who call themselves "adventurers." Clerics and wizards are uncommon, but many adventuring companies of at least four or five members count at least one such in their group. All other classes combined make up perhaps 10-20% of the adventuring types at large. Only the largest of adventuring companies, those sporting 10-12 members, are likely to have a character such as a druid or paladin in their ranks.
3) I'm guessing you are looking specifically for the Swords & Sorcery "Conan/Red Sonja" type feel for the game. Are demi-humans just as rare as adventurers?
Humans are the dominant civilization in the Flanaess and demi-humans are not a common sight. "Respectable" elves and dwarves do not associate with humans unless it is to ally themselves against evil forces, and that is the extent of most of their interactions. It is quite unusual to see them elsewhere, however when you do, it is often in the company of adventurers, as they fit in very few other places among the human societies. Usually demi-humans such as elves and dwarves join adventuring companies in the quest of rooting out evil places or in search of forgotten lore or knowledge of their ancestors, but they can have other motivations as well, especially dwarves who are quite greedy when it comes to precious metals and gemstones. Halflings associate with humans in a few places, but mostly live in their own communities, very much like the Hobbits in Middle-Earth. Halflings are exceptionally rare when it comes to adventuring, but those few that do tend to excel at it and display immense bravery and cunning. They often do it for the excitement as much as the prospect of wealth.
Within the City of Greyhawk, the population is over 90% human. Of the fraction that are demi-human, many keep to themselves as much as possible, as they tend to stick out. Some humans even outright fear them. You might encounter a prosperous dwarf shopkeeper who deals in curios and valuable items (he could also be a fence). You could hear of a halfling baker whose biscuits and muffins are to die for. There could be a reclusive elf wizard whom everyone seems to know of but very few have actually met. These individuals often face prejudice in public however, so they tend to avoid being in the public eye.
4) I am not 100% sure just how _low_ you're aiming for low magic... would a character with a dream of flying and/or owning/building a flying vessel be on par with the Greyhawk Experience?
Such a thing would be a bit unrealistic within the setting (although there will always be those with unrealistic dreams). Practically-speaking, there is no such thing as a "flying machine" or even a magical flying vessel. Such things are the stuff of legend, perhaps powerful magic possessed by the ancient Suloise Imperium or Baklunish Empire. But for all the extraordinary magic possessed by those civilizations, their magic ended up destroying both civilizations in an event known today as the "Twin Cataclysms," leaving very few signs of their existence remaining. A powerful archmage named Zagyg was once Lord Mayor of the City of Greyhawk, but he grew insane over the years of his tenure. Eventually he disappeared completely, leaving a number of questionable projects in the works and a fortress called Castle Greyhawk which today is said to be infested with monsters. It is for reasons like this that many people fear magic. This fear is the chief reason magic does not currently flourish in the Flanaess today. Those who know magic tend to keep it to themselves. Even Greyhawk's University of Magical Arts is shrouded in mystery. The pyramidal structure has no outwardly visible entrance, and no one seems to know just how the students of this place, whomever they might be, gain access to the interior.
The city is lit at night by oil lamps (or in the poorer districts by torchlight or not at all), not by everburning lanterns. People travel by conventional means such as horse and cart, boat, or walking, not by taking flying carpets or riding pegasi through the skies. Courts of law rely upon testimony and evidence to determine the truth, not divination magic. There are no shops that deal regularly in magic items (although in rare cases one might stumble across a magical item for sale in a shop almost by accident); finding a buyer or seller for a magic item is a difficult process as only the wealthiest could afford such items, and even then finding someone who wants an item might be a difficult process. Most people would not even think of using magic to accomplish everyday tasks. And the open use of magic in public is frowned upon. There are even strict laws about the use of magic in public; any spell or magic item that causes collateral damage to the city or its citizens in any way (including magic that manipulates the mind or divines secrets) can subject the user to harsh fines, imprisonment, or even (in the most serious of cases), severing of the fingers and removal of the tongue.
There are certainly exceptions to the rule. Wizards might use prestidigitation to entertain a crowd. A cleric might be called upon to remove disease if a terrible blight has struck the city and quarantine has failed. But these are still exceptions. Such things are not common by any means.
