There are many difficulties in being a slave. These increase exponentially if your master happens to be a mage who acts like an oversized baby.
The first difficulty will most likely come from your master's inability to not make a mess. You'll have to clean his alchemy room regularly and fight off whatever monstrosity he's brought to life while picking out materials that can be salvaged.
You'll also have to chase his books around the library for the head servant to de-animate. Not only so, but you also have to avoid certain places because the master keeps misplacing his charms and most of those contain offensive spells.
You'll also have to dedicate most of your free time to learning a bit of magic to protect yourself from the plants in the garden and from the pets.
There's also the errands which may or may not take up to a week of travel to complete because teleportation circles are the bane of any life.
There are times you'll have to perform your duties in the form of a strange creature or as the wrong gender or with an inverted body but those don't have anything on the absolute worst. When the country is at war.
The King will send an envoy to your mage which will enrage him and send him into a tantrum. The head servant, of course, will convince the mage to accept the invitation to the castle which will worsen the tantrum and give you more messes to deal with.
Soon after the mage and his servant leaves, leaving you in charge of a castle free of a tantrum throwing mage, you may relax and cast anti-dirt spells on the wall because for some reason no one thought to cast them earlier.
You'll have to wrangle the monsters of the castle into obeying you or, what I do, ignore them until the mage returns.
If you're as unfortunate as I am, you'll have a run in with mages sent to steal from your mage and regardless of how well you know the castle, you will be caught and you will be killed.
As one can imagine from such a bratty master, you'll inevitably be dragged from death to clean up messes.