In order the Power of Attorney to be valid, you have to be mentally capable because the consequences of this document are important since you give the complete authority to the Attorney to act on your behalf for different financial transactions. The POA ends if you are not mentally capable to manage your wealth and affairs.
The Power of Attorney might have some restrictions, like the Attorney can only sells a house, a deadline when the POA won’t be valid or outline and limit the authority on the document.
Sometimes the POA is used overseas, in this case you must apostille/authenticate/certificate the Power of Attorney by the Global Affairs/Foreign Affairs Ottawa JLAC (Authentication Services Section) and finally legalized by the embassy/consulate of the country in which the Power of Attorney will be used because the jurisdiction of that country won’t accept this document if it did not follow these steps to be valid and recognised oversees. If the POA is a copy, then it must be notarized by a Notary Public or a lawyer before the authentication/Apostille/Certification by the DFEAT (Department of Foreign Affairs Canada/ JLAC-Authentication Services Section).