Income from training children and selling membership cards. Raising children may be the biggest and most stable income. Income from selling membership cards. The key to making money in the arena is rent. If the rent is expensive, it will be difficult to make a profit. I have a friend who runs an arena. It is meaningless to rent more than 40 thousand a year. It would be much better if the house were my own. Badminton has a high unit price per hour and a large amount of exercise. Whether you can play can make you run two steps, giving people a feeling that you can exercise better and lose weight. This may be the reason why it attracts more amateurs than table tennis.