Regarding the money, I think someone in another thread came up with the idea that a good life is changed into currency when you die. Not actual money that can buy you anything (because Meche was poor) but the kind that can only be used to get a travel package. That idea needs developing a little, but it's worth a thought. It certainly sounds absurd that people would still be buried with real money in the Land of the Living because when Manny briefly visits it, it looks like it's around 1950's.
All the lines about being buried with money, wanting a dead rich saint etc. might have been just expressions of speech. For example, it's possible that all this talk about money is just Reaper slang for a good life. After all, Domino said he sold a Double N Ticket to a nun (which he of course didn't, but it's possible because Manny didn't question it) and nuns aren't generally that rich.