Nairobi, Aug. 15 -- At 37, John Mathegi says he feels stronger than he did in his 20s. As he approaches 40, he is betting that the physical and financial foundation he is building today will give him the freedom to navigate life on his own terms.

For a man who has no plans to marry, Mathegi imagines a future where he is physically fit, financially secure, and free to travel the world without having to depend on anyone.

"I bet I will have made a lot of money by then. The essence of life is to live a good life, and I have been working on building that base, body-wise and financially," he chuckles, in his soft voice.

It is not difficult to see that his ambitions extend beyond the words. He is a sharp dresser, drives a sleek black sedan, a...