TL;DR = "Normals" (NPCs) are in their late 20s or 30s by Wizard 1, and maybe 5th by 60. PCs can be 18ish, and live bright short lives...
My 5e campaign is around a bunch of "late teenagers", with a "grizzled veteran" warrior. They all started at 1st level, with different backstories. The veteran was a retired Marine, healing after the injury that got him discharged. The youngest, 16, is of course the spellcaster - but he is a warlock who had failed out of wizard training (and no idea where his powers come from). The second oldest just turned 20, the bard, who has been "wasting his potential" performing in a dive bar near the river. In this world, "normal" people hit 2nd or 3rd level in their career; exceptional people hit 4th, and legendary hit 5th. PCs quickly become "mythic"!
Magic in the world has been growing for the last 400 years. Initially only Mageborn (sorcerers) could wield magic. Then "talented" people could learn, after 40-60 years of study, meditation, and practice. Then "talented" people could pull off 1st level spells (i.e. Wizard 1 or 2) in "only" 20 years. Next, "anyone off the street" could become a wizard (in 40ish years), while talented people could graduate to Wizard 1 in about 10 years. At campaign start, talented people can become Wizards in about 10-15 years (i.e. about age 18-24). [Sorcerers meanwhile hit level 1 at puberty, whether they want to or not... Mageborn is more of a PF2e archetype now, adding 1 level of Sorcerer ability to your character every 2 class levels, even if you choose Wizard or Sorcerer.] So if you wield arcane magic, you are a graduate of the Towers - a Wizard, with PCs being younger than "normals" - or you are a Mageborn noble with the blood of ancients. Warlocks are anathema - charlatans at best, cheaters and devil-worshippers... or "Blood thieves" at worst. People who covet magic, but aren't Mageborn, and are unable or unwilling to put in the work to become a Wizard (or can't pay for it, yay feudalistic capitalism.), and look for a shortcut.