Sidekick Rules

Wizards of the Coast released rules for Sidekicks in an Unearthed Arcana article you can read here. We're going to use a modified version of these rules.
Sidekicks gain levels in a sidekick class through the following downtime activity. They do not gain levels any other way.
Downtime Activity: Train a Sidekick. You can spend 10 days of downtime to train a sidekick. The sidekick must be a creature of CR 1 or less. This gives the sidekick a level in a sidekick class of your choice. The sidekicks total number of class levels cannot exceed your own number of class levels minus two.
Training a sidekick bonds it to your character. No other character can train your sidekick or bring it on an adventure without your permission. This prevents another player from getting your sidekick killed while you're absent from the game.
Tagging Along. When you start a session, your party can bring a sidekick of yours along with you if your party size would be three or less without it. Sidekicks are controlled by the player of the character the sidekick is bonded to, but the DM can take over when it becomes necessary for the plot. Sidekicks count as party members when dividing up XP, even though they don't gain any benefit from XP (Because the sidekick made the fight easier, individual characters receive fewer XP.)