I second all the comments by the above posters!
Believe me, 50-something is not too old --there is a tremendous need for nurses in this country, and there are many area of nursing for you to choose from. One advantage of nursing is that it allows many more options than other fields - many hospital specialities, outpatient and clinic facilities, etc, etc, etc. Once you finish school you will be able to find the right niche for you.
Will nurses still be able to get decent jobs in their 60's? After graduating from school, you should be able to work as long as you want to-- one of my OR nurse colleagues at work is in her early 60's, and she works rings around many people 20 or 30 years younger than she is!
Better late than never-- I just graduated from an RN-mobility program (RN to BSN program) at the age of 48, and plan to graduate with my master's at 50, so Never think that you are too old. It's not too late to follow your dreams!!!! As shygirl said, the years are going to go by anyway.
Good luck-- you can do it!