I want to run a photography studio in my spare time. What should I do? How feasible is it?

Spare time is impossible (as if it were completely impossible). The biggest difficulty in life is not what you get, but what you choose. If you want to do something, especially at the beginning, you must put your heart and soul into it to have a chance of success. If you are half-hearted, your enterprise, like 99% SMEs in China, has an average life span of only 3.5 years.