There is no legal requirement that you health care agent be someone who lives near you. However, filling that role long distance can be a challenge so finding someone who lives nearby is always a plus. But location is just one factor among many.
When considering distance it is important to remember that the real issue with distance is how quickly they could be at the health care facility interacting directly with the doctors providing your care and giving meaningful directions. Factors for that could include travel time but might also include how much notice they would need to leave their job and family responsibilities in a crisis. A single sister with a flexible job in San Francsico might be a better bet on that front that a single mom with young children in Pasco who can't get off work without several weeks notice.
It is also important that you don't let this factor alone trump all the rest. It should be the best person serving in this role not only the closest. If in doubt, it is possible if working with an attorney to have an interim agent appointed who can serve until the best agent can be at the care center. That might be a local friend or family member who could be in communication with the permanent agent and be gathering information and making imminent decisions until the agent can really assess the situation on their own.
If you have questions about how to select and assign the best health care agent for your unique situation, please contact us for a free 1/2 hour consultation at (206) 459-1908 or firstname.lastname@example.org.