Why Delaying Retirement is Good for You
Even if you weren't a tennis instructor for your primary working lifetime you can make it a post retirement paying avocation. I have known many that have done just this.
Your post retirement approach to work
I knew a schoolteacher who retired from teaching but he had also volunteered to coach tennis at his school so he already had some experience. It turned out to be a good thing for him and the community as he taught until he passed away in his early 90's.
In another case I had a friend that liked tennis and became a strong player but made his living in the corporate world. After his retirement he went looking for something to do that didn't involve the stress he had lived most of his working life. He found tennis teaching and community tennis programs were the ideal thing for him to do and also made a fair amount of income as well. He finally took a full retirement when health problems caused him to move into an independent and then later an assisted living facility, but until that time he had a very active life.
Anyone that loves tennis can find some way to get involved
In addition to these two examples I know many people in various walks of life from physical therapists, military retirees, teachers, and former coaches in other sports who are tennis enthusiasts plan to take up teaching as a part time solution to retirement activity and income. If you are contemplating such an approach my main suggestion is to get started with teaching skills by taking training and to get involved on a volunteer basis for county programs or local tennis associations. You could even set up something in your local community but keep in mind that insurance is always the issue so getting some sort of certification with insurance that is offered makes good sense. It will also help you decide if this lifestyle is for you.
Keep Teaching
Finally, if you are already a tennis teacher the best way to stay active is to keep teaching. Sure, you don't want to put in fifty hour weeks on the court, but how about scaling down and teaching twenty hours. When I say twenty hours I mean combined group and private lessons because if you're doing twenty hours a week of private lessons you're still putting a serious effort into your job.
I have a couple of tennis pro friends that share with me the challenges of reaching the age of sixty and thinking they can still maintain the teaching schedule they may have had for the past thirty years. It simply isn't possible without wearing yourself down and eventually out. I ran into this myself as injuries and repetitive use problems seemed to show up much more often as I headed toward my sixties.
A modest approach
Do a slow fade. Just allow your schedule to slow down to match your financial and health needs. If you can get by with only fifteen or twenty hours a week on the court then do it. The nice thing is that you'll still get the benefits of social engagement if you spend time in the community teaching tennis and sharing what you've learned. If you still have management responsibilities at a club then you can focus more on those and less on teaching.
Share the Game
You can also use the opportunity to mentor others that want to get into teaching and since you're no longer in competition for business it might be one of the best things you can do to help keep tennis growing in your community. I have taken the opportunity many times to bring others into teaching, coaching, and just volunteering in tennis. It's a good thing for everyone involved.
It is a perfect retirement atmosphere
The environment for tennis is conducive to fun and interaction which are essential parts of staying happy and healthy. If you can make some money at the same time to help support your retirement needs then you've accomplished the ideal which is to find something that keeps you involved and yet allows you to live a comfortable life.