Unfortunately, there comes a time when we are often faced with helping our parents with their financial decisions as they get older. It's important that we recognize these times so that we can avoid mistakes or worse, being subject to a scam. One of the things you can do is have a Durable Power of Attorney appointed by your parent which gives you all the authority that they would have to operate for them. They have to have capacity to do this. It's important it be written and signed, and procedures properly followed.
A second avenue is having a trust formed. In fact, that can be done where the parent is actually the trustee for a period of time, but as they lose control or the ability to handle their affairs, the trustee has a legal and fiduciary obligation to take care their affairs them.
The final and the most drastic method is conservatorship, which actually sometimes referred to as a guardianship, requires a court order determining that the parent is no longer able to take care of their affairs and the court appoints someone to do so.