I've never tried this before but its possible I've heard to time-lock some BTC coins when you are sending them.
I think he wants to lock in the form of his fiat money instead of bitcoin
Bank cd wouldn't work for me because you can still withdraw that money with penalty.
afaik, any financial investment will always have a termination/cancelation/breach clause in a legal agreement paper
without such clauses, the agreement paper would be deemed incomplete in a legal perspective