I agree with the majority of what the other posters have said. It's not too old to start IF (and it's a big "if") you are in excellent physical health and have realistic expectations. You'll have to deal with some potential problems that are "solvable" but sometimes difficult. I have known people in their 40's and 50's begin nursing careers and be successful and happy with their choice -- but I have also seen some who were not really prepared to deal with some of the issues and who where therefore, disappointed with their choice.
Here are just a few things to think about:
1. In most areas of the country, new grads start their careers working in an inpatient setting (hopistal, nursing home, etc.) -- a facility that needs workers 24/7. That means that you have to be prepared to work your share of the night shifts, weekends, holidays, etc. While most people say they know that going in ... some people find that they are really not wanting to work those hours when the time comes. They also find that their middle-aged bodies don't tolerate those hours as well as they younger bodies. And don't forget, entry-level staff nurse jobs often involve being on your feet for 12 straight hours, lifing, moving equipment, etc.
Suggestion: Do your homework and find out about job opportunities for new grads in your area. You might even try to do a trial run of some 12-hour rotating shifts and see how your body tolerates it before investing in the education.
2. Some mature students find it extremely frustrating to go to school with students much younger than they are. They find their fellow students immature and difficult to get along with. The same goes for many of the instructors. Some will be younger and less mature than you -- less mature in their ability to make judgments about running their classes, make decisions about handling the student issues and politics of teaching, etc. That can add to the stress of a mature student who may have trouble learning from a teacher he/she does not respect as a teacher -- even though that instructor may be a competent nurse.
3. As an older new grad, your preceptors, your boss, etc. may well be younger and less personally mature than you are. Again, while they will be more skilled in their nursing care, they may be less skilled at handling some of the interpersonal dynamics -- and having to be in a subordinate position to these less mature nurses may add to your stress.
If you can handle these issues, then don't let your age get in the way. However, don't be a "Pollyanna" and let unrealistic expectations lead you down a path you are going to regret. Assess your physical abilities and your willingness to deal with these very real and difficult potiential problems before deciding. Don't gloss over the negatives just because you find the positives appealing. If you enter the field with realistic expectations, you'll have the greatest chance of success.