The Canadian College of Linguistics has successfully trained graduates of all ages who have successfully secured ESL employment.
Some schools around the world prefer younger ESL teachers while others prefer more seasoned ESL teachers, and a lot will accept everything in between. If you are a mature teacher, it is best to research the retirement age in your countries of choice to ensure that you are eligible to work there. You may be required to purchase your own medical or travel insurance and most positions will require a current medical examination. If you are a younger teacher, you will need to showcase your passion for teaching and adventure. Schools will also like to see that you have a fun and friendly personality, and that you are mature enough to handle the responsiblty that teaching requires.
A simple internet search will provide a lot of information about this topic.