(2) Intellectual property rights. It can be copyright, patent, trademark, etc., and then collect the value of intellectual property rights. For example, in the decade before Lu Xun's death, his main income was royalties, and in that era, his royalties could ensure that he lived above the middle class.
(3) Knowledge products and services. Earn profits by selling knowledge products, serve more people and institutions, and directly provide products and services to the society. In fact, the knowledge payment we are talking about now refers to this.