He's already spent the $3bn funding that was supposed to deliver the rocket to the moon and back.
You can go to the official govenrment website and look at the contract, it tells you exactly how much has been paid out and how much has not been. The money is getting out as SpaceX hits development milestones.
I don't remember, exactly but about 2.x billion $ were paid out so far. The money is spread over 40ish milestones. And they have done like 25 or so by now.
To get the full pay out, they will be required to land on the moon and take off again. Those are likely the last couple milestones.