Most adults have heard of something called a Power of Attorney (POA). This is a legal document wherein Person A (the "principal") gives Person B (the "agent") the legal authority to act on behalf of Person A and carry out specific actions, as set forth in the document.
Such authority is in addition to all the powers that a legally competent individual would have. In other words, if Dad signs a POA naming Son as his agent, Dad still has all the powers he had before signing it: Dad has not given up his authority to sign checks, access bank accounts, transfer property, etc. Instead, he has extended his authority to another person. So now either Dad or Son can sign checks, access accounts, etc.
Since POA forms are so widely available from online sources, is it all right to avoid going to see an attorney and instead simply purchase a POA online? As an attorney who prepared POA forms for 25 years, I can definitely say that, while some online forms are better than others, none of them is worth paying for. Here's why:
Can't customize: First of all, there is no interview process to determine what type of clauses are appropriate to insert into the document and which clauses to omit or modify. For example, should there be authority to make gifts to certain family members, and if so, how should that be determined and limited? Might some consideration be given to the possibility that the principal (usually the parent) may need to move to a nursing home at some point and need to apply for Medicaid? If so, it is crucial to include very specific Medicaid-planning-related clauses in the POA document.
No professional counsel: Second, there is no one with experience to assist you in determining who should be the agent (typically one of the children), who should be the successor agent, whether the Powers should be "immediate" or "springing," and if so, under what circumstances, etc.
No legal witnesses: Third, there is no one witnessing the signing, who can vouch for the mental capacity of the principal (parent), so as to avoid a later claim that the form is invalid. (Yes, sometimes other family members become resentful of the named agent and try to invalidate the POA document.)
Questionable quality: Finally, the online forms vary tremendously in quality and thoroughness, and the lay person will have no way to judge good from bad. Merely "looking official" is not good enough. A POA is a very powerful document; if you sign one, you are giving someone else the power to empty out your bank account, sell your house out from under you, possibly make gifts to people you don't approve of, move you from one residence to another, etc.
Note that the cost to have a lawyer-prepared POA is usually quite modest, under $200 in many cities. Be sure to find an attorney who does a lot of estate planning and/or elder law work, for the most appropriate advice and forms.