Do I need to have a good credit to handle a friend's bank account through a bank P O A?

A power of attorney is only the right to sign for a person in either a general or a limited manner.

You can be the worst criminal serving time in prison and still be given a power of attorney. You can be filing bankrutpcy, owe everyone in town.
Now I would not want someone who is not trust worthy to have ability to write checks from my account. But there is no restrictions, only they be someone you officially appointin writing.

And you are not handling, you are signing and writing checks on their behalf. Our friend would still have full control of his account but you would be able to act on his behalf.