@Nikkei_Simmer - I can't quote chapter and verse from the Sunset Valley tax code, upon which I imagine the tax codes of the other worlds are based. But seems to me it depends on which world one wants to live in. Playable ghosts are residents who happen to have an occult state. They get to own property, earn income, and use municipal services like public schools and the library (don't they?), be protected by the police and fire departments, enjoy city parks, so they get to pay taxes. If they live in some other spiritual world, then the rules of that world would apply.
Disclaimer: I'm starting to not have the slightest idea what I am talking about here... :p