[1/5] THE GOVERNMENT: Humans part of the RAI branch. There are many positions (occupations) within the government branch. The actual hunters themselves, scientists, analysts, informants, weapon developers, the simple book keepers, etc. Feel free to use your creativity here.
[Unlimited] THE CIVILIANS: Humans who are not part of the government nor posses the witch gene. They can have any occupation and they are generally unaware of witches, ghouls or the RAI unless they are somehow exposed to them and sucked into their mess.
[2/5] THE WITCHES: Humans born with the witch gene. They may or may not have had their awakening yet. Generally on the surface, witches are normal members of society. They can have any occupation they want. (Criminal is also considered an occupation.)
[2/3] THE GHOULS: Non-human/Demons. Ghouls do not generally have a "occupation" unless they are trying to blend in with people which is very rare. They get their money and things by stealing or exploiting humans.
RAI (Radical Allied Intelligence) is a secret government branch who's claimed purpose is to fight against the harmful use of witchcraft and to protect the general population. Behind the scenes however, many witches are captured alive and experimented on. Because not much is known about the witch gene there is a desire to study the subjects and perhaps one day to create an artificial "witch gene."
The government keeps a database of awakened witches and uses various tactics and weapons to hunt them. RAI has yet to develop a substance that suppresses the witch gene and so the most reliable weapon is actually intellect and stealth. (NOTE: RAI, aside from being an acronym, relates to the word MOIRAI but the information has never been publicly disclosed)
Witches are humans who were born with the "witch gene." Not much is known about it as it tends to skip generations without any sort of structure and some carriers go their entire lives without being aware of it. Humans born with the "witch gene" can awaken their powers at any point in their life. Some awaken their powers as children, some as adults and some never knew they even had it. All witches have a "core" element which is the major source of their power. Most awakenings happen when a carrier of the gene has an extreme exposure to their core element. (Fire, Air, Earth, Lightning or Water) Witches are mortal and can be killed (thought its a much more difficult task) but they cannot be slain by their own element. Fire cannot kill a dragon.
Ghouls, demons, devils whichever name you know them by, they are sinister beings outside of the human world; though sometimes they reside in it. Most Ghouls are conjured up by witches for a purpose but are not easy to control or persuaded to do a witch's bidding. More often than not, bringing a ghoul to the human world is not a good idea. Ghouls cannot go between planes as they choose. Once called up to the human world by a witch they stay there until the conjuring witch undoes the spell or someone else manages to shove them back down to Hell. Just like witches, Ghouls have a core element. (Fire, Air, Earth, Lightning or Water)