My father passed away. I am the only living relative my mother has. If she became incapacitated - would I need a Power of Attorney?

Yes, that is one way that you can be enabled to deal with her financial affairs. Another way is for your mother to enter into a fully funded revocable living trust naming you as successor trustee. For many reasons this is a better way of dealing with incapacity, although most people probably use the durable power of attorney. Having said that, if your mother grants you that power, make sure that it is the new version of the durable power of attorney, as the statute in Florida was significantly changed in October of 2011. This is specific to Florida law and does not constitute legal advice as the facts presented are anonymous and incomplete. This is intended for general education only and does not create an attorney-client relationship. This should not be relied on and you must seek your own attorney client relationship.