My father will pretty much sign anything as requested. He just isn't interested in taking care of his business anymore. I would like to legally make it a requirement that the POA's signature must accompany his signature to make it valid to alleviate the potential of his signing whatever he is asked that may not be in his best interest.
I would encourage you first to look up the rules for POA in your own state.
Then I would encourage you to go to an Elder Law Attorney. Buying an hour of time for your questions is cheap at any price.
The POA is either fully enforced and activated by proof of incompetence legally or it is not. If it is, watch what you wish for because you are in charge of everything from account, investments and etc. and must go to each Bank, Utility Company, Insurance company and etc. to give over your POA papers. They will be fully enforced by several letters from MDs of incompetency and an order of the court that you are signee for all legal matters.
Then no matter what, when or where your Dad attempts to do anything from banking to scams, his funds will be protected, as you are the signee on accounts, not him.
It isn't an either/or situation, and once done you are stuck with files and folders for each and every account and entity and each and every penny in and out of all accounts.
So it's a problem to decide when, where, why and how to do all this.
If your Dad's funds are now endangered by his incompetency it is time to act.
My brother and I did this while he was still competent and lucid but with a dx. of probable early Lewy's. He was very frightened of himself and for his assets. He made me POA active and Trustee of Trust. I was signee for everything and all bills and notices came to me as his POA. He got nothing and I handled it all, giving him a monthly accounting, keeping all records. It took a solid year to set up. Every entity wants something different. It's even worse now I hear with outsourcing becoming the American Way.
Sorry. What a trip, huh? If you do this expect a year on the phone, arranging, worrying, hassling, becoming quite anxious. Once it's all done, and you are recognized as the one responsible, it's easy. And my brother only improved after all the anxiety of the costs of daily living were off his mind, and on my own. I did, by the by, provide him with his own small spending account. Which amazingly, from his ALF, he only GREW in amount.
A "regular" PoA must be activated first by whatever criteria is named in the document (usually 1 official diagnosis of sufficient impairment by their doctor).