According to the prerequisites of the Squire Feat you can take the feat at level 3, but you cannot have a squire more than 3 levels lower than you. The Leadership Feat does not provide rules for attracting cohorts lower than level 1 (which would be pretty much useless anyway, but I digress).
My question is whether you can gain any mechanical benefits (acquire a squire) with a level 3 character who has the Squire feat?
Evidence to consider:
- The Feat was errata'd from prereq of level 4 to prereq of level 3. This could be taken two ways. Either they intended level 3 characters to be able to take the feat and gain the advantage of it, or they intended level 4 characters to be able to have squires (which would have been impossible with a level 4 prereq, as the feat is not a combat feat and there is no progression that gets you a new feat at 4th level)
- The source of the 3rd-level errata Patrick Renie claims that he would homerule it to be effective at 3rd level