Building an electronic mall to buy and sell things is actually building a third-party trading platform. After the traffic of this platform is large, it can be profitable by collecting membership registration fees, advertising fees, transaction fees and other means. At present, the law of e-commerce is relatively backward, and it can be operated without a business license. But to be big, you need a business license. Taobao and Alibaba are both third-party trading platforms.
As for whether you can build your own website to sell things, such as clothes. There is no clear e-commerce law at present. People who sell things on Taobao basically don't have a business license, but if you want to be big, you'd better get a business license. Its business scope is "e-commerce" rather than "e-commerce information consultation".