I exchange my services (helping you build a barn) in return, you render a service (help me build mine). Equal exchange of value. After the barns are raised, and animals fed, due to help from children (earning sustenance, and roof over head, clothes on back in exchange for giving them life, and provision until age of ability), we harvest lumber to build furniture, purchase or produce fabrics for clothing or bed clothes, and other accoutrements, and sell these to eachother in exchange for other products or services, or sell them to the outside world. Not very socialist if you ask me.