A 85 b:

Both the Acolyte and the Apprentice Mage are CR 1/4, and you can't get much lower than that. Neither is listed as typically preparing Detect Magic, but both cast as prepared casters, from class spell lists that include that spell, so either could prepare it if they chose.

Also CR 1/4 is the specific individual Volothamp Geddarm, who also casts as a 1st-level wizard, and is explicitly listed as typically preparing Detect Magic.