I don't have an issue with "you cannot prestige while you have any debt"
But I think the second requirement, meeting a donation target, is odd in itself.
I think being able to prestige whenever you have zero debt is good, and leave it to the player's judgement for when to prestige (preferably, you clearly tell the player how many prestige points they will get before they prestige, and being able to see the prestige tree before doing so is always great/useful if I am aiming for specific upgrade(s).