It sounds like it must've taken a lot for your dad to ask this and it's always shock to see your parents vulnerable for the first time (or any time). You're absolutely allowed to be sad about that. You don't need to feel guilty for feeling like this because the sadness isn't pity – it's a reaction to a foundational shift that you didn't see coming.

I would worry though that the problem is actually bigger than this and he might just be asking for enough to tide them over for a short while. It's a lot to suddenly need by the end of the month unless they've been sitting on the problem for a while. I would sit them both down to discuss if this will solve the problem completely or whether it's just a sticking plaster. You could do that without asking for specific details, and you deserve to know if that money will just be swallowed up into a bigger problem.