I have looked in a few areas for this cheat but have yet to see it listed. So I am risking embarassment once more in the hopes it will help others enjoy the game.
Firefighters and Ghost Hunters Cheat:
As usual, on main menu you must turn on testingcheatsenabled true.
Then you simply start your game. Go to any house that is not an established NPC building (example: Firehouse, Townhall). Hold down your shift key and and left click. You will then get the option to spawn various types of jobs.
Your permitted job spawning options change as you increase your firefighting skills. When you first join you only get the option small housefire but this changes as you are more experienced. I have seen small housefire, large housefire and earthquakes.
If this has been mentioned then I apologize for my redundancy.
Quick point on the ghosthunting side. I imagine the types will also change for experienced ghosthunters but I have yet to explore this. When I discovered the trick I was already a very experienced ghosthunter who got bored waiting for the ghosts to catch.
New information for you:
At level 4 of the firefighting career I was given the option of gnome invasion and also saw large fires.
NPC buildings do spawn jobs as long as you are focused on the correct buildings. Hospital and Citizens Warehouse are the only ones I currently see.