Reversionary Interest

The key word here is "revert."

For example:

"For $10,000, you can use the walkway between my house and the beach for 10 years; after that time period, that right to use my (amazing) walkway reverts back to me and only me, and you're left using that other walkway—the one covered in rusty nails and rabid wolves. This forces you to negotiate again, and all the circumstances are different. For instance, now I want $20,000 instead of $10,000."

Reversionary interests apply to vanilla investments too. That is, "Cousin Billy Joe, you get the interest on these bonds and the rent from these apartments until your mama Cousin Louloubelle dies; at that point, the dough from these two vehicles reverts back to me."