There are three types of apprentices, herbal apprentices(just a cool name for medic apprentices), rhea apprentices(Info: ), and warrior apprentices. Kits will get a dream at 5 moons from a StarClan cat named Fallow about which kind of apprentice they'll be. This is COMPLETELY randomized, I use a spin the wheel app, so don't come at me if you get an apprentice type you didn't want. There are limits to how many herbal apprentices there are, just like there are a limit to how many medics there are. (4 medics and 4 herbal apps). For rheas, I will probably limit it at some point, but if there aren't enough rheas to train the rhea apps, then likely the leader will train them. Warrior apprentices are well... warrior apprentices. There's no limit.
Apprentice Accessories: When you become an apprentice you get an accessory! Rheas have a different accessory(see the info about rheas for the stuff), but usually you will get a bluebonnet(MarineClan) or rose head(ConstellationClan) depending on your clan. This accessory is to be worn behind the ear. It is your choice whether or not to take off this accessory as a fully-trained warrior/medic, but rheas have to keep theirs.