My parents rented a shop of about 20 square meters next to the entrance of the vegetable market, with a monthly rent of 4000 yuan. What business can they do to make money?

I'll give you a business that really makes money and suits your parents. I have personally experienced that noodles, dumpling skins and chaotic skins can be made, as long as you study the ratio of noodles for a few days. Everything else can be operated by machines. The machine is inexpensive and easy to operate. Profits are also optimistic. According to the rent and location you mentioned, more than 10 thousand a month is the least. Secondly, my father rented a stall in the vegetable market to sell beef and mutton himself. If you can find a wholesale butcher who kills beef and mutton, you can earn 7.8 yuan a catty. It won't be too tired. My father is doing it alone. He is 68 years old and can earn 200,000 to 300,000 a year. The input cost is also the lowest. I hope he can help you.