My wife's family is chinese and asked us to stay with them

Hi , my wife is chinese and her parents asked us to come and stay with them. To look after their health. My wife's father has a restaurant is it possible under s1 type that i come and "help" in the restaurant so he can stop working and take care of his health (i am a chef from trade), without getting paid. More of a helping hand. Thank you so much for your insight.
Also is it possible to stay more than a year with this S1 type or do i have to enter / re enter china everytime i need to extend the visa?