Tell that to Jimmy Connors. The knees go by 40 and, yes, you can still play but not like golf. Too much wear and tear.
Tennis is a good pick though because most people wouldn’t know 7 or 8 of the top 10 players in the world if they walked in the room. It has a wealthy niche audience and excellent endorsement cash flow. Who watches Wimbledon? 3% of the population? 1%? But they can run Mercedes ads etc and still do well because of the demographics.
Worst is football. 3 year careers. More than half are bankrupt within 10 years. Lifetime of brain damage and limping. If you look at the teams, 95% of active defensive players are now black. No cries for diversity?
As I said, of all the sports golf is the most lucrative, safest, less likely to be hassled, and can play forever.
Yes, if you're good enough, there's a lot of money to be made hitting that little white ball. About two hundred players make a very good living from golf; about fifty players make an extremely good living from golf, and maybe ten or twenty are billionaires from golf. And if you're good enough (again) you can transition to the Senior (uh... Champions) Tour and keep winning money into your sixties (a la Bernhard Langer...).