I have told one of my Mormon friends that in the event that she outlives me, it is OK with me for her to baptize me after my death in case I find myself to be dead and surrounded by spirits informing me that the Mormons were right all along. I don't expect this to happen. I expect that if she outlives me, I will be immersed in liquid nitrogen without consciousness of any kind, and she'll show up at a temple and spend however long making herself feel better about this fact. But if the Mormons were right, I'd be glad of the assist, since baptism posthumous or otherwise appears to be a prerequisite for some of the best goodies.

This sort of arrangement - differing beliefs, but agreement conditional on either belief being true - allows for slightly weird but ethically harmless non-monetary transactions like that. (I assume no one would have trouble with: a Rapture believer who was friends with an atheist getting that atheist to agree to take care of eir pets in the event of Rapture, for free.)

Incorporating money makes it weird. But if it's legal and ethical to give something away, it's usually legal and ethical to sell it. The exceptions are, as far as I know, all obviously stupid legislative artifacts (prostitution); or prohibited to protect the seller, not the prospective buyer (organs); or things considered by the legislating body to be outright harmful, as opposed to just useless, to have/use (drugs). A contract stating that someone will look after your pets if you are Raptured is none of the above.