Hi - my name is XXXXX XXXXX I'm a Criminal Law litigation attorney. Thanks for your question.
IF you are his power of attorney (general, durable power of attorney), then you can do ANYTHING you wish with any of his property. For all legal purposes, you are him on paper.
However, as POA, you have a fiduciary duty not to waste his money, or commit self-dealing by taking his property/money and converting it to your own use.
So, if you were to place his money in your account, you need to keep meticulous records to prove you didn't use it or do anything illegal or improper just in case a relative challenges your actions.
You may want to speak with an estate planning attorney, who could set up a trust account or some other fund to house the money that would allow you to access it if need be, but it would keep the property out of your personal holdings.