Once a person has a diagnosis of alzheimers, you are unable to apply to get legal power of attorney. You can however apply for a guardianship order through SATS. I have worked in aged care for 14 years as a registered nurse. One of my main jobs was to interview residents and their families prior to entry. My one and only suggestions to you and your family, is to make sure you do not leave it too late to start looking for care options. Waiting lists in care facilities are long, especially for males. You could be waiting anywhere up to a year for a suitable bed and unfortunately that means people hit a crisis situation and the person ends up bouncing around the public health system. You can apply for waitlisting once the person has recieved an ACAT assessment, they will either get approval for high or low care. Although the prognosis for people with Alzheimers is roughly 7 years it can be effected by numerous other things.
My auntie was diagnosed with it at the age of 45, she passed away 9 years later.

There is medication (aricept)that can be taken to help slow the process however the person would need to be assessed by a gerontologist as the medication needs approval before it is dispensed. The medication does only work for a short period of time.

All the best with it all, I am sorry to hear you are going through this.