I have 2 DC at university. They both need me to guarantee their rent next year. This year, one of them has managed his money badly and has needed top-ups to pay his monthly rent (on top of the money he already receives, which his rent and living costs are budgeted from). The other one has managed her money fine. They both have the same amount of money to live on each week after rent, though DD lives in a more expensive city (both outside London).
For next year I've said to them that I will guarantee the rent but only if they transfer to me from their loans and other money the rent amount, which I will then pay on their behalf and will leave them to manage their living money. They both flatly refuse and say this is unnecessary. In the case of DD, I can see her point. In the case of DS, I'm very unhappy about it as he has already shown he can't/won't budget.
If I were to be called on under either guarantee, I wouldn't have the money to pay as have no savings. So I would like the security of knowing the rent will definitely be paid and not used up ahead of time on other expenses. Most people I know had their parents pay their rent and just transfer them living money, and this is how my friends with DC at uni do it too. My DC say no one does this and it's unreasonable.
What is reasonable here?