Is it legal to marry some one and get paid for it
So that the person can get there inherited money
That they were only supposed to get when they get married.
The money is in a trust fund and can't be used until this person gets married

Is there a stipulation that this person has to stay married for a certain period? Would this person get divorced once he/she has claimed the money? Would this person give a cut of the inheritance to the person he/she marries (for being cooperative)?

Not that I know of,but what if I don't get the money from him when he gets it? What would I do about that?

You'd sue him for breach of contract, the Court would laugh at both of you, you'd be married with no money.

Cool thanks