This is the short writeup I'm usng as a primer for my Golarion-based 13th Age Hangouts game, The Seven Dragon Candle Adventuring Society. I cribbed the first three or so paragraphs with minor changes, so it's not an entirely original idea.
Heroes are rare, and famous: their deeds resound through every nation, kingdom and town, inspiring countless teenagers to train themselves up and become adventurers. Adventurers unfortunately, are as common as mud; in fact there are far more adventurers, than places that need them. Even assuming that an adventuring band can get together, find a place to practice, get the time away from their real jobs to practice and weather the various personality conflicts that arise, most simply lack the talent to get anywhere.
The vast majority of adventuring bands disband after a few sessions of flailing around chasing dire gophers from a farmer's yard, even if they can get such a basic job, since the competition is fierce. More talented adventuring bands get to guard caravans, act as security for warehouses, or if they're particularly attractive, protect the parties of wealthy nobles. And even there, the agents the adventuring bands use to find work will rarely be able to wrangle enough payment for the party members to quit their regular jobs as field hands, alchemists assistants, or innkeeper's daughters. Many agents also prefer to build up their own adventuring bands; slick looking, perfectly accoutered parties that look good at a festival even if their tactics and abilities are uninspired.
Only a tiny proportion of adventuring bands become even a little famous, and only a few every generation hit the heights of herodom. You're one of those plucky adventuring bands, sneaking away in the afternoon for combat practice, scraping together silver to buy an old sword. You may not know how hard the competition is, or you may not care, because you've got the tales of the great heroes ringing in your ears, the drive to succeed... maybe.
The Seven Dragon Candle Adventuring Society is really just a group of people in a little village in Varisia who like to think of themselves as adventurers. Children from the village look up to members of the group. They play at being adventurers in the shadows of farmhouses and inns, even though the only adventurers they know personally are members of the Society. Some join when they are old enough, deciding that playing at being an adventurer isn't as fun as actually being one. As members get older and more experienced, they leave the village and the Society and move on to bigger and better things. Some return and inspire with stories of their exploits. Some have darker stories, tales that scare some away from idea of the adventuring life. But those that stick with the group? The bonds they form with each other are inseparable, and their own little adventures wonderful and amazing in their own way. However, while they may stay with the Seven Dragon Candle Adventuring Society for years, many feel the call of something greater, and eventually they soon find themselves on the dirt road out of town, looking for adventure and excitement...